Anti-aircraft warfare

See also:Surface-to-air missile

Several terms redirect here. For other uses, seeFlak (disambiguation),Ack Ack (disambiguation),andAnti-Aircraft (video game).

Anti-aircraft warfareis the counter toaerial warfareand includes "all measures designed to nullify or reduce the effectiveness of hostile air action".It encompasses surface-based, subsurface (submarine-launched), and air-based weapon systems, in addition to associated sensor systems, command and control arrangements, and passive measures (e.g.barrage balloons). It may be used to protectnaval,ground,andair forcesin any location. However, for most countries, the main effort has tended to behomeland defence.Missile defenceis an extension of air defence, as are initiatives to adapt air defence to the task of intercepting any projectile in flight.

Artist's rendition of short and long range AA systems used by the DutchJoint Ground-based Air Defence Command

Most modern anti-aircraft (AA) weapons systems are optimized for short-, medium-, or long-range air defence, although some systems may incorporate multiple weapons (such as bothautocannonsandsurface-to-air missiles). ‘Layered air defence’ usually refers to multiple ‘tiers’ of air defence systems which, when combined, an airborne threat must penetrate in order to reach its target; This defence is usually accomplished via the combined use of systems optimized for either short-, medium-, or long-range air defence.

In some countries, such as Britain and Germany during theSecond World War,theSoviet Union,and modern NATO and the United States, ground-based air defence and air defence aircraft have been under integrated command and control. However, while overall air defence may be for homeland defence (including military facilities), forces in the field, wherever they are, provide their own defences against airborne threats.

Until the 1950s, guns firing ballistic munitions ranging from 7.62 mm (.30 in) to 152.4 mm (6 in) were the standard weapons; guided missiles then became dominant, except at the very shortest ranges (as withclose-in weapon systems,which typically userotary autocannonsor, in very modern systems, surface-to-air adaptations of short-rangeair-to-air missiles,often combined in one system with rotary cannons).

Terminology

It may also be calledcounter-air,anti-air,AA,flak,layered air defenceorair defence forces.

The termair defencewas probably first used by the UK whenAir Defence of Great Britain(ADGB) was created as aRoyal Air Forcecommand in 1925. However, arrangements in the UK were also called "anti-aircraft", abbreviated asAA,a term that remained in general use into the 1950s. After theFirst World Warit was sometimes prefixed by "light" or "heavy" (LAA or HAA) to classify a type of gun or unit. Nicknames for anti-aircraft guns include "AA", "AAA" or "triple-A" (abbreviations of "anti-aircraft artillery" ), "flak" (from the GermanFlugzeugabwehrkanone), "ack-ack" (from thespelling alphabetused by the British for voice transmission of "AA" );and "archie" (a World War I British term probably coined byAmyas Borton,and believed to derive via theRoyal Flying Corps,from themusic-hallcomedianGeorge Robey's line "Archibald, certainly not!").

NATO defines anti-aircraft warfare (AAW) as "measures taken to defend a maritime force against attacks by airborne weapons launched from aircraft, ships, submarines and land-based sites".In some armies the termall-arms air defence(AAAD) is used for air defence by nonspecialist troops. Other terms from the late 20th century include "ground based air defence" (GBAD) with related terms "short range air defense"(SHORAD) andman-portable air-defense system(MANPADS). Anti-aircraft missiles are variously calledsurface-to-air missiles,( "SAMs" ) and surface-to-air guided weapons (SAGWs). Examples are theRIM-66 Standard,Raytheon Standard Missile 6,or theMBDA Astermissile.

Non-English terms for air defence include the GermanFlakorFlaK(Fliegerabwehrkanone,'aircraft defence cannon',also cited asFlugabwehrkanone), whence Englishflak,and the Russian termProtivovozdushnaya oborona(Cyrillic:Противовозду́шная оборо́на), a literal translation of 'anti-air defence', abbreviated as PVO.In Russian, the AA systems are calledzenitnye(i.e., 'pointing tozenith') systems. In French, air defence is calledDéfense contre les aéronefs (DCA),aéronefmeaning 'aircraft'.

The maximum distance at which a gun or missile can engage an aircraft is an important figure. However, many different definitions are used and unless the same definition is used, performance of different guns or missiles cannot be compared. For AA guns only the ascending part of the trajectory can be usefully used. One term is "ceiling", the maximum ceiling being the height a projectile would reach if fired vertically, not practically useful in itself as few AA guns are able to fire vertically, and the maximum fuse duration may be too short, but potentially useful as a standard to compare different weapons.

The British adopted "effective ceiling", meaning the altitude at which a gun could deliver a series of shells against a moving target; this could be constrained by maximum fuse running time as well as the gun's capability. By the late 1930s the British definition was "that height at which a directly approaching target at 400 mph [640 km/h] can be engaged for 20 seconds before the gun reaches 70 degrees elevation".

General description

The essence of air defence is to detect hostile aircraft and destroy them. The critical issue is to hit a target moving in three-dimensional space; an attack must not only match these three coordinates, but must do so at the time the target is at that position. This means that projectiles either have to be guided to hit the target, or aimed at the predicted position of the target at the time the projectile reaches it, taking into account the speed and direction of both the target and the projectile.

Throughout the 20th century, air defence was one of the fastest-evolving areas of military technology, responding to the evolution of aircraft and exploiting technology such as radar, guided missiles and computing (initially electromechanical analogue computing from the 1930s on, as with equipment described below). Improvements were made to sensors, technical fire control, weapons, and command and control. At the start of the 20th century these were either very primitive or non-existent.

Initially sensors were optical and acoustic devices developed during World War I and continued into the 1930s,but were quickly superseded by radar, which in turn was supplemented byoptoelectronicsin the 1980s. Command and control remained primitive until the late 1930s, when Britain created an integrated systemfor ADGB that linked the ground-based air defence of the British Army'sAnti-Aircraft Command,although field-deployed air defence relied on less sophisticated arrangements. NATO later called these arrangements an "air defence ground environment", defined as "the network of ground radar sites and command and control centres within a specific theatre of operations which are used for the tactical control of air defence operations".

Rules of engagement are critical to prevent air defences engaging friendly or neutral aircraft. Their use is assisted but not governed byidentification friend or foe(IFF) electronic devices originally introduced during theSecond World War.While these rules originate at the highest authority, different rules can apply to different types of air defence covering the same area at the same time. AAAD usually operates under the tightest rules.

NATO calls these rules "weapon control orders" (WCO), they are:

• Weapons free:weapons may be fired at any target not positively recognised as friendly.
• Weapons tight:weapons may be fired only at targets recognised as hostile.
• Weapons hold:weapons may only be fired in self-defence or in response to a formal order.

Until the 1950s, guns firing ballistic munitions were the standard weapon; guided missiles then became dominant, except at the very shortest ranges. However, the type of shell or warhead and its fuzing and, with missiles, the guidance arrangement were and are varied. Targets are not always easy to destroy; nonetheless, damaged aircraft may be forced to abort their mission and, even if they manage to return and land in friendly territory, may be out of action for days or permanently. Ignoring small arms and smaller machine-guns, ground-based air defence guns have varied in calibre from 20 mm to at least 152 mm.

Ground-based air defence is deployed in several ways:

• Self-defence by ground forces using their organic weapons, AAAD.
• Accompanying defence, specialist air defence elements accompanying armoured or infantry units.
• Point defence around a key target, such as a bridge, critical government building or ship.
• Area air defence, typically "belts" of air defence to provide a barrier, but sometimes an umbrella covering an area. Areas can vary widely in size. They may extend along a nation's border, e.g. theCold WarMIM-23 HawkandNikebelts that ran north–south across Germany, across a military formation's manoeuvre area, or above a city or port. In ground operations air defence areas may be used offensively by rapid redeployment across current aircraft transit routes.

Air defence has included other elements, although after the Second World War most fell into disuse:

• Tetheredbarrage balloonsto deter and threaten aircraft flying below the height of the balloons, where they are susceptible to damaging collisions with steel tethers.
• Cables strung across valleys, sometimes forming a "curtain" with vertical cables hanging from them.
• Searchlightsto illuminate aircraft at night for both gun-layers and optical instrument operators. During World War II searchlights became radar controlled.
• Largesmoke screenscreated by large smoke canisters on the ground to screen targets and prevent accurate weapon aiming by aircraft.

Passive air defence is defined by NATO as "Passive measures taken for the physical defence and protection of personnel, essential installations and equipment in order to minimise the effectiveness of air and/or missile attack".It remains a vital activity by ground forces and includes camouflage and concealment to avoid detection by reconnaissance and attacking aircraft. Measures such as camouflaging important buildings were common in the Second World War. During the Cold War the runways and taxiways of some airfields were painted green.

Organization

While navies are usually responsible for their own air defence—at least for ships at sea—organisational arrangements for land-based air defence vary between nations and over time.

The most extreme case was the Soviet Union and this model may still be followed in some countries: it was a separate service, on a par with the army, navy, or air force. In the Soviet Union, this was calledVoyska PVO,and had both fighter aircraft, separate from the air force, and ground-based systems. This was divided into two arms,PVO Strany,the Strategic Air defence Service responsible for Air Defence of the Homeland, created in 1941 and becoming an independent service in 1954, andPVO SV,Air Defence of the Ground Forces. Subsequently, these became part of the air force and ground forces respectively.

At the other extreme, theUnited States Armyhas anAir Defense Artillery Branchthat provides ground-based air defence for both homeland and the army in the field; however, it is operationally under theJoint Force Air Component Commander.Many other nations also deploy an air-defence branch in the army. Some, such as Japan or Israel, choose to integrate their ground based air defence systems into their air force.

In Britain and some other armies, the single artillery branch has been responsible for both home and overseas ground-based air defence, although there was divided responsibility with theRoyal Navyfor air defence of the British Isles inWorld War I.However, during theSecond World War,theRAF Regimentwas formed to protect airfields everywhere, and this included light air defences. In the later decades of theCold Warthis included theUnited States Air Force's operating bases in the UK. All ground-based air defence was removed from Royal Air Force (RAF) jurisdiction in2004.The British Army'sAnti-Aircraft Commandwas disbanded in March 1955,but during the 1960s and 1970s the RAF's Fighter Command operated long-range air-defence missiles to protect key areas in the UK. During World War II, theRoyal Marinesalso provided air defence units; formally part of the mobile naval base defence organisation, they were handled as an integral part of the army-commanded ground based air defences.

The basic air defence unit is typically a battery with 2 to 12 guns or missile launchers and fire control elements.These batteries, particularly with guns, usually deploy in a small area, although batteries may be split; this is usual for some missile systems. SHORAD missile batteries often deploy across an area with individual launchers several kilometres apart. When MANPADS is operated by specialists, batteries may have several dozen teams deploying separately in small sections; self-propelled air defence guns may deploy in pairs.

Batteries are usually grouped into battalions or equivalent. In the field army, a light gun or SHORAD battalion is often assigned to a manoeuvre division. Heavier guns and long-range missiles may be in air-defence brigades and come under corps or higher command. Homeland air defence may have a full military structure. For example, the UK's Anti-Aircraft Command, commanded by a fullBritish Army generalwas part of ADGB. At its peak in 1941–42 it comprised three AA corps with 12 AA divisions between them.

History

Earliest use

The use of balloons by the U.S. Army during the American Civil War compelled the Confederates to develop methods of combating them. These included the use of artillery, small arms, and saboteurs. They were unsuccessful, and internal politics led the United States Army'sBalloon Corpsto be disbanded mid-war. The Confederates experimented with balloons as well.

Turks carried out the first ever anti-airplane operation in history during theItalo-Turkish war.Although lacking anti-aircraft weapons, they were the first to shoot down an airplane by rifle fire. The first aircraft to crash in a war was the one of Lieutenant Piero Manzini, shot down on August 25, 1912.

The earliest known use of weapons specifically made for the anti-aircraft role occurred during theFranco-Prussian Warof 1870. After thedisaster at Sedan,Paris was besiegedand French troops outside the city started an attempt at communication viaballoon.GustavKruppmounted a modified 1-pounder (37 mm) gun – theBallonabwehrkanone(Balloon defence cannon) orBaK— on top of a horse-drawn carriage for the purpose of shooting down these balloons.

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  Ballonabwehrkanoneby Krupp
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  Ballonabwehrkanoneby Krupp
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  Ballonabwehrkanoneon the Prussian corvetteNymphe1872
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  20 mm Becker-Oerlikon Model 1917 AA-gun

By the early 20th century balloon, or airship, guns, for land and naval use were attracting attention. Various types of ammunition were proposed, high explosive, incendiary, bullet-chains, rod bullets and shrapnel. The need for some form of tracer or smoke trail was articulated. Fuzing options were also examined, both impact and time types. Mountings were generally pedestal type but could be on field platforms. Trials were underway in most countries in Europe but only Krupp, Erhardt,VickersMaxim, andSchneiderhad published any information by 1910. Krupp's designs included adaptations of their 65 mm 9-pounder, a 75 mm 12-pounder, and even a 105 mm gun. Erhardt also had a 12-pounder, while Vickers Maxim offered a 3-pounder and Schneider a 47 mm. The French balloon gun appeared in 1910, it was an 11-pounder but mounted on a vehicle, with a total uncrewed weight of two tons. However, since balloons were slow moving, sights were simple. But the challenges of faster moving aeroplanes were recognised.

By 1913 only France and Germany had developed field guns suitable for engaging balloons and aircraft and addressed issues of military organisation. Britain's Royal Navy would soon introduce theQF 3-inchandQF 4-inchAA guns and also hadVickers 1-pounder quick firing "pom-poms"that could be used in various mountings.

The first US anti-aircraft cannon was a 1-pounder concept design byAdmiral Twiningin 1911 to meet the perceived threat of airships, that eventually was used as the basis for the US Navy's first operational anti-aircraft cannon: the3-inch/23 caliber gun.

First World War

1909 vintage Krupp 9-pounder anti-aircraft gun

A Canadian anti-aircraft unit of 1918 "taking post"

A French anti-aircraft motor battery (motorized AAA battery) that brought down aZeppelinnear Paris. From the journalHorseless Age,1916.

On the 30th of September, 1915, troops of theSerbian Armyobserved three enemy aircraft approachingKragujevac.Soldiers fired at them with shotguns and machine-guns but failed to prevent them from dropping 45 bombs over the city, hitting military installations, the railway station and many other, mostly civilian, targets in the city. During the bombing raid,privateRadoje Ljutovacfired his cannon at the enemy aircraft and successfully shot one down. It crashed in the city and both pilots died from their injuries. The cannon Ljutovac used was not designed as an anti-aircraft gun; it was a slightly modified Turkish cannon captured during theFirst Balkan Warin 1912. This was the first occasion in military history that a military aircraft was shot down withground-to-airartillery fire.

The British recognised the need for anti-aircraft capability a few weeks before World War I broke out; on 8 July 1914, theNew York Timesreported that the British government had decided to "dot the coasts of the British Isles with a series of towers, each armed with two quick-firing guns of special design," while "a complete circle of towers" was to be built around "naval installations" and "at other especially vulnerable points". By December 1914 theRoyal Naval Volunteer Reserve(RNVR) was manning AA guns and searchlights assembled from various sources at some nine ports. TheRoyal Garrison Artillery(RGA) was given responsibility for AA defence in the field, using motorised two-gun sections. The first were formally formed in November 1914. Initially they usedQF 1-pounder "pom-pom" s(37 mm versions of theMaxim Gun).

A Maxim anti-aircraft machine gun in the anti-aircraft museum in Finland, 2006

All armies soon deployed AA guns often based on their smaller field pieces, notably the French 75 mm and Russian 76.2 mm, typically simply propped up on some sort of embankment to get the muzzle pointed skyward. TheBritish Armyadopted the 13-pounder quickly producing new mountings suitable for AA use, the13-pdr QF 6 cwt Mk IIIwas issued in 1915. It remained in service throughout the war but 18-pdr guns were lined down to take the 13-pdr shell with a larger cartridge producing the13-pr QF 9 cwtand these proved much more satisfactory.However, in general, these ad hoc solutions proved largely useless. With little experience in the role, no means of measuring target, range, height or speed the difficulty of observing their shell bursts relative to the target gunners proved unable to get their fuse setting correct and most rounds burst well below their targets. The exception to this rule was the guns protecting spotting balloons, in which case the altitude could be accurately measured from the length of the cable holding the balloon.

The first issue was ammunition. Before the war it was recognised that ammunition needed to explode in the air. Both high explosive (HE) andshrapnelwere used, mostly the former. Airburst fuses were either igniferious (based on a burning fuse) or mechanical (clockwork). Igniferious fuses were not well suited for anti-aircraft use. The fuse length was determined by time of flight, but the burning rate of the gunpowder was affected by altitude. The British pom-poms had only contact-fused ammunition.Zeppelins,being hydrogen-filled balloons, were targets for incendiary shells and the British introduced these with airburst fuses, both shrapnel type-forward projection of incendiary "pot" and base ejection of an incendiary stream. The British also fitted tracers to their shells for use at night. Smoke shells were also available for some AA guns, these bursts were used as targets during training.

German air attacks on the British Isles increased in 1915 and the AA efforts were deemed somewhat ineffective, so aRoyal Navygunnery expert, Admiral SirPercy Scott,was appointed to make improvements, particularly an integrated AA defence for London. The air defences were expanded with more RNVR AA guns, 75 mm and 3-inch, the pom-poms being ineffective. The naval 3-inch was also adopted by the army, theQF 3-inch 20 cwt(76 mm), a new field mounting was introduced in 1916. Since most attacks were at night, searchlights were soon used, and acoustic methods of detection and locating were developed. By December 1916 there were 183 AA sections defending Britain (most with the 3-inch), 74 with the BEF in France and 10 in the Middle East.

AA gunnery was a difficult business. The problem was of successfully aiming a shell to burst close to its target's future position, with various factors affecting the shells' predicted trajectory. This was called deflection gun-laying, where "off-set" angles for range and elevation were set on the gunsight and updated as their target moved. In this method, when the sights were on the target, the barrel was pointed at the target's future position. Range and height of the target determined fuse length. The difficulties increased as aircraft performance improved.

The British dealt with range measurement first, when it was realised that range was the key to producing a better fuse setting. This led to theheight/range finder(HRF), the first model being theBarr & StroudUB2, a two-metreoptical coincident rangefindermounted on a tripod. It measured the distance to the target and the elevation angle, which together gave the height of the aircraft. These were complex instruments and various other methods were also used. The HRF was soon joined by the height/fuse indicator (HFI), this was marked with elevation angles and height lines overlaid with fuse length curves, using the height reported by the HRF operator, the necessary fuse length could be read off.

However, the problem of deflection settings — "aim-off" — required knowing the rate of change in the target's position. Both France and the UK introduced tachymetric devices to track targets and produce vertical and horizontal deflection angles. The French Brocq system was electrical; the operator entered the target range and had displays at guns; it was used with their 75 mm. The British Wilson-Dalby gun director used a pair of trackers and mechanical tachymetry; the operator entered the fuse length, and deflection angles were read from the instruments.

By the start ofWorld War I,the 77 mm had become the standard German weapon, and came mounted on a large traverse that could be easily transported on a wagon. Krupp 75 mm guns were supplied with an optical sighting system that improved their capabilities. The German Army also adapted a revolving cannon that came to be known to Allied fliers as the "flaming onion"from the shells in flight. This gun had five barrels that quickly launched a series of 37 mm artillery shells.

As aircraft started to be used against ground targets on the battlefield, the AA guns could not be traversed quickly enough at close targets and, being relatively few, were not always in the right place (and were often unpopular with other troops), so changed positions frequently. Soon the forces were adding variousmachine-gunbased weapons mounted on poles. These short-range weapons proved more deadly, and the "Red Baron"is believed to have been shot down by an anti-aircraftVickers machine gun.When the war ended, it was clear that the increasing capabilities of aircraft would require better means of acquiring targets and aiming at them. Nevertheless, a pattern had been set: anti-aircraft warfare would employ heavy weapons to attack high-altitude targets and lighter weapons for use when aircraft came to lower altitudes.

The No. 1 Mark III Predictor that was used with theQF 3.7-inch AA gunwas a mechanical computer.

Shooting with anti-aircraft gun in Sweden 1934

Interwar years

World War I demonstrated that aircraft could be an important part of the battlefield, but in some nations it was the prospect of strategic air attack that was the main issue, presenting both a threat and an opportunity. The experience of four years of air attacks on London by Zeppelins andGotha G.Vbombers had particularly influenced the British and was one of if not the main driver for forming an independent air force. As the capabilities of aircraft and their engines improved it was clear that their role in future war would be even more critical as their range and weapon load grew. However, in the years immediately after World War I, the prospect of another major war seemed remote, particularly in Europe, where the most militarily capable nations were, and little financing was available.

Four years of war had seen the creation of a new and technically demanding branch of military activity. Air defence had made huge advances, albeit from a very low starting point. However, it was new and often lacked influential 'friends' in the competition for a share of limited defence budgets. Demobilisation meant that most AA guns were taken out of service, leaving only the most modern.

However, there were lessons to be learned. In particular the British, who had had AA guns in most theatres in action in daylight and used them against night attacks at home. Furthermore, they had also formed anAnti-Aircraft Experimental Sectionduring the war and accumulated large amounts of data that was subjected to extensive analysis. As a result, they published the two-volumeTextbook of Anti-Aircraft Gunneryin 1924–1925. It included five key recommendations for HAA equipment:

• Shells of improved ballistic shape with HE fillings and mechanical time fuses
• Higher rates of fire assisted by automation
• Height finding by long-base optical instruments
• Centralised control of fire on each gun position, directed by tachymetric instruments incorporating the facility to apply corrections of the moment for meteorological and wear factors
• More accurate sound-location for the direction of searchlights and to provide plots for barrage fire

Two assumptions underpinned the British approach to HAA fire; first, aimed fire was the primary method and this was enabled by predicting gun data from visually tracking the target and having its height. Second, that the target would maintain a steady course, speed and height. This HAA was to engage targets up to 24,000 ft (7.3 km). Mechanical time fuses were required because the speed of powder burning varied with height, so fuse length was not a simple function of time of flight. Automated fire ensured a constant rate of fire that made it easier to predict where each shell should be individually aimed.

In 1925 the British adopted a new instrument developed by Vickers. It was a mechanicalanalogue computer- the Predictor AA No 1. Given the target height, its operators tracked the target and the predictor produced bearing, quadrant elevation and fuse setting. These were passed electrically to the guns, where they were displayed on repeater dials to the layers who "matched pointers" (target data and the gun's actual data) to lay the guns. This system of repeater electrical dials built on the arrangements introduced by British coast artillery in the 1880s, and coast artillery was the background of many AA officers. Similar systems were adopted in other countries and for example the later Sperry M3A3 in the US, was also used by Britain as the Predictor AA No 2. Height finders were also increasing in size; in Britain, the seven-foot optical base World War IBarr & StroudUB 2stereoscopic rangefinderwas replaced by the nine-foot optical base UB 7 and the eighteen-foot optical base UB 10 (only used on static AA sites). Goertz in Germany and Levallois in France produced five m (16 ft) instruments. However, in most countries the main effort in HAA guns until the mid-1930s was improving existing ones, although various new designs were on drawing boards.

From the early 1930s eight countriesdeveloped radar;these developments were sufficiently advanced by the late 1930s for development work onsound-locating acoustic devicesto be generally halted, although equipment was retained. Furthermore, in Britain the volunteerObserver Corpsformed in 1925 provided a network of observation posts to report hostile aircraft flying over Britain. Initially radar was used for airspace surveillance to detect approaching hostile aircraft. However, the GermanWürzburg radarput into use in 1940 was capable of providing data suitable for controlling AA guns, and the BritishRadar, Gun Laying, Mark I,was designed to be used on AA gun positions and was in use by 1939.

TheTreaty of Versaillesprevented Germany having AA weapons, and for example, the Krupps designers joined Bofors in Sweden. Some World War I guns were retained and some covert AA training started in the late 1920s. Germany introduced the 8.8 cm FlaK 18 in 1933, the 36 and 37 models followed with various improvements, but ballistic performance was unchanged. In the late 1930s the10.5 cm FlaK 38appeared, soon followed by the 39; this was designed primarily for static sites but had a mobile mounting, and the unit had 220 V 24 kW generators. In 1938 design started on the12.8 cm FlaK.

Britain had successfully tested a new 3.6-inch gun, in 1918. In 1928 a 3.7-inch (94 mm) gun became the preferred solution, but it took six years to gain funding. Production of theQF 3.7-inch gunbegan in 1937; this gun was used on mobile carriages with the field army and transportable guns on fixed mountings for static positions. At the same time the Royal Navy adopted a new4.5-inch (113 mm) gunin a twin turret, which the army adopted in simplified single-gun mountings for static positions, mostly around ports where naval ammunition was available. The performance of the new guns was limited by their standard fuse No 199, with a 30-second running time, although a new mechanical time fuse giving 43 seconds was nearing readiness. In 1939 a machine fuse setter was introduced to eliminate manual fuse setting.

The US ended World War I with two 3-inch AA guns and improvements were developed throughout the inter-war period. However, in 1924 work started on a new 105 mm static mounting AA gun, but only a few were produced by the mid-1930s because by this time work had started on the 90 mm AA gun, with mobile carriages and static mountings able to engage air, sea and ground targets. The M1 version was approved in 1940. During the 1920s there was some work on a 4.7-inch which lapsed, but revived in 1937, leading to a new gun in 1944.

While HAA and its associated target acquisition and fire control was the primary focus of AA efforts, low-level close-range targets remained and by the mid-1930s were becoming an issue.

Until this time the British, at RAF insistence, continued their use of World War I machine guns, and introduced twin MG mountings for AAAD. The army was forbidden from considering anything larger than.50-inch.However, in 1935 their trials showed that the minimum effective round was an impact-fused 2 lb HE shell. The following year they decided to adopt theBofors 40 mmand atwin barrel Vickers 2-pdr(40 mm) on a modified naval mount. The air-cooled Bofors was vastly superior for land use, being much lighter than the water-cooled "pom-pom", and UK production of the Bofors 40 mm was licensed. The Predictor AA No 3, as theKerrison Predictorwas officially known, was introduced with it.

The 40 mm Bofors had become available in 1931. In the late 1920s theSwedish Navyhad ordered the development of a 40 mm naval anti-aircraft gun from the Bofors company. It was light, rapid-firing and reliable, and a mobile version on a four-wheel carriage was soon developed. Known simply as the40 mm,it was adopted by some 17 different nations just before World War II and is still in use today in some applications such as on coastguard frigates.

Rheinmetall in Germany developed an automatic 20 mm in the 1920s and Oerlikon in Switzerland had acquired the patent to an automatic 20 mm gun designed in Germany during World War I. Germany introduced the rapid-fire2 cm FlaK 30and later in the decade it was redesigned by Mauser-Werke and became the 2 cm FlaK 38.Nevertheless, while 20 mm was better than a machine gun and mounted on a very small trailer made it easy to move, its effectiveness was limited. Germany therefore added a 3.7 cm. The first, the3.7 cm FlaK 18developed by Rheinmetall in the early 1930s, was basically an enlarged 2 cm FlaK 30. It was introduced in 1935 and production stopped the following year. A redesigned gun 3.7 cm FlaK 36 entered service in 1938, it too had a two-wheel carriage.However, by the mid-1930s the Luftwaffe realised that there was still a coverage gap between 3.7 cm and 8.8 cm guns. They started development of a 5 cm gun on a four-wheel carriage.

After World War I the US Army started developing a dual-role (AA/ground) automatic 37 mm cannon, designed byJohn M. Browning.It was standardised in 1927 as the T9 AA cannon, but trials quickly revealed that it was worthless in the ground role. However, while the shell was a bit light (well under 2 lbs) it had a good effective ceiling and fired 125 rounds per minute; an AA carriage was developed and it entered service in 1939 as the37 mm gun M1.It proved prone to jamming, and was eventually replaced in AA units by the Bofors 40 mm. The Bofors had attracted attention from the US Navy, but none were acquired before 1939.Also, in 1931 the US Army worked on a mobile anti-aircraft machine mount on the back of a heavy truck having four.30 calibre water-cooled machine guns and an optical director. It proved unsuccessful and was abandoned.

The USSR introduced a new 76 mmM1931in 1937, an 85 mmM1938and developed the37 mm M1939 (61-K),which appears to have been copied from the Bofors 40 mm. A Bofors 25 mm, essentially a scaled down 40 mm, was also copied as the25 mm M1939.

During the 1930s solid-fuel rockets were under development in the Soviet Union and Britain. In Britain the interest was for anti-aircraft fire, it quickly became clear that guidance would be required for precision. However, rockets, or "unrotated projectiles"as they were called, could be used for anti-aircraft barrages. A two-inch rocket using HE or wire obstacle warheads - theZ battery- was introduced first to deal with low-level or dive bombing attacks on smaller targets such as airfields. The three-inch was in development at the end of the inter-war period.

Naval aspects

WWI had been a war in which air warfare blossomed, but had not matured to the point of being a real threat to naval forces. The prevailing assumption was that a few relatively small caliber naval guns could manage to keep enemy aircraft beyond a range where harm might be expected. In 1939 radio controlledtarget dronesbecame available to the US Navy in quantity allowing a more realistic testing of existing anti-aircraft suites against actual flying and manoeuvring targets.The results were sobering to an unexpected degree.

The United States was still emerging from the effects of theGreat Depressionand funds for the military had been sparse to the degree that 50% of shells used were still powder fused.The US Navy found that a significant portion of its shells were duds or low order detonations (incomplete detonation of the explosive contained by the shell). Virtually every major country involved in combat in World War II invested in aircraft development. The cost of aircraft research and development was small and the results could be large.So rapid was the performance leaps of evolving aircraft that the BritishHigh Angle Control System(HACS) was obsolete and designing a successor very difficult for the British establishment.Electronics would prove to be an enabler for effective anti-aircraft systems and both the US and UK had a growing electronics industry.

In 1939 radio controlled drones became available to actually test existing systems in British and American service. The results were disappointing by any measure. High-level manoeuvring drones were virtually immune to shipboard AA systems. The US drones could simulate dive bombing which showed the dire need for autocannons. Japan introduced powered gliders in 1940 as drones but apparently was unable to dive bomb.There is no evidence of other powers using drones in this application at all. It may have caused a major underestimation of the threat and an inflated view of their AA systems.

Second World War

Poland's AA defences were no match for the German attack, and the situation was similar in other European countries.Significant AAW (Anti-Air Warfare) started with theBattle of Britainin the summer of 1940.QF 3.7-inch AA gunsprovided the backbone of the ground-based AA defences, although initially significant numbers ofQF 3-inch 20 cwtwere also used. The Army's Anti-aircraft command, which was under operational command ofRAF Fighter Commandwithin Air Defence GB, grew to 12 AA divisions in three AA corps.Bofors 40 mm gunsentered service in increasing numbers. In addition, the RAF regiment was formed in 1941 with responsibility for airfield air defence, eventually with Bofors 40 mm as their main armament. Fixed AA defences, using HAA and LAA, were established by the Army in key overseas places, notablyMalta,Suez CanalandSingapore.

While the 3.7-inch was the main HAA gun in fixed defences and the only mobile HAA gun with the field army, theQF 4.5-inch gun,manned by artillery, was used in the vicinity of naval ports and made use of the naval ammunition supply. The 4.5-inch at Singapore had the first success in shooting down Japanese bombers. Mid warQF 5.25-inch naval gunsstarted being emplaced in some permanent sites around London. This gun was also deployed in dual-role coast defence/AA positions.

German88 mmflak gun in action against Allied bombers

Germany's high-altitude needs were originally going to be filled by a 75 mm gun fromKrupp,designed in collaboration with their Swedish counterpartBofors,but the specifications were later amended to require much higher performance. In response Krupp's engineers presented a new 88 mm design, theFlaK 36.First used in Spain during theSpanish Civil War,the gun proved to be one of the best anti-aircraft guns in the world, as well as particularly deadly against light, medium, and even early heavy tanks.

After theDambusters raidin 1943 an entirely new system was developed that was required to knock down any low-flying aircraft with a single hit. The first attempt to produce such a system used a 50 mm gun, but this proved inaccurate and a new 55 mm gun replaced it. The system used a centralised control system including both search and targetingradar,which calculated the aim point for the guns after considering windage and ballistics, and then sent electrical commands to the guns, which usedhydraulicsto point themselves at high speeds. Operators simply fed the guns and selected the targets. This system, modern even by today's standards, was in late development when the war ended.

German soldier manning anMG34anti-aircraft gun in WWII

The British had already arranged licence building of the Bofors 40 mm, and introduced these into service. These had the power to knock down aircraft of any size, yet were light enough to be mobile and easily swung. The gun became so important to the British war effort that they even produced a movie,The Gun,that encouraged workers on the assembly line to work harder. The Imperial measurement production drawings the British had developed were supplied to the Americans who produced their own (unlicensed) copy of the 40 mm at the start of the war, moving to licensed production in mid-1941.

AUSAAFConsolidated B-24 Liberatorhit by flak over Italy, 10 April 1945

Service trials demonstrated another problem however: that ranging and tracking the new high-speed targets was almost impossible. At short range, the apparent target area is relatively large, the trajectory is flat and the time of flight is short, allowing to correct lead by watching the tracers. At long range, the aircraft remains in firing range for a long time, so the necessary calculations can, in theory, be done by slide rules—though, because small errors in distance cause large errors in shell fall height and detonation time, exact ranging is crucial. For the ranges and speeds that the Bofors worked at, neither answer was good enough.

BritishQF 3.7-inchgun inLondonin 1939

The solution wasautomation,in the form of a mechanical computer, theKerrison Predictor.Operators kept it pointed at the target, and the Predictor then calculated the proper aim point automatically and displayed it as a pointer mounted on the gun. The gun operators simply followed the pointer and loaded the shells. The Kerrison was fairly simple, but it pointed the way to future generations that incorporated radar, first for ranging and later for tracking. Similar predictor systems were introduced by Germany during the war, also adding radar ranging as the war progressed.

US coast guardsmen in the South Pacific man a 20 mm anti-aircraft cannon

A plethora of anti-aircraft gun systems of smaller calibre was available to the German Wehrmacht combined forces, and among them the 1940-originFlakvierlingquadruple-20 mm-autocannon-based anti-aircraft weapon system was one of the most often-seen weapons, seeing service on both land and sea. The similarAlliedsmaller-calibre air-defence weapons of the American forces were also quite capable. Their needs could cogently be met with smaller-calibre ordnance beyond using the usual singly-mountedM2.50 calibermachine gun atop a tank's turret, as four of the ground-used "heavy barrel" (M2HB) guns were mounted together on the American MaxsonM45 Quadmountweapon (as a direct answer to theFlakvierling), which were often mounted on the back of ahalf-trackto form theM16 Multiple Gun Motor Carriage.Although of less power than Germany's 20 mm systems, the typical four or five combat batteries of an Army AAA battalion were often spread many kilometres apart from each other, rapidly attaching and detaching to larger ground combat units to provide welcome defence from enemy aircraft.

Indian troops manning aBren light machine gunin an anti-aircraft mount in 1941

AAA battalions were also used to help suppress ground targets. Their larger90 mm M3 gunwould prove, as did the eighty-eight, to make an excellent anti-tank gun as well, and was widely used late in the war in this role. Also available to the Americans at the start of the war was the120 mm M1 gunstratosphere gun,which was the most powerful AA gun with an impressive 60,000 ft (18 km) altitude capability, however no 120 M1 was ever fired at an enemy aircraft. The 90 mm and 120 mm guns continued to be used into the 1950s.

TheUnited States Navyhad also put some thought into the problem, When the US Navy began to rearm in 1939 in many ships the primary short ranged gun was the M2.50 caliber machine gun. While effective in fighters at 300 to 400 yards this is point blank range in naval anti-aircraft ranges. Production of the Swiss Oerlikon 20 mm had already started to provide protection for the British and this was adopted in exchange for the M2 machine guns.From December 1941 to January 1942, production had risen to not only cover all British requirements but also allowed 812 units to be actually delivered to the US Navy.By the end of 1942 the 20 mm had accounted for 42% of all aircraft destroyed by the US Navy's shipboard AA. However, the King Board had noted that the balance was shifting towards the larger guns used by the fleet. The US Navy had intended to use the British pom-pom, however, the weapon required the use of cordite which BuOrd had found objectionable for US service.Further investigation revealed that US powders would not work in the pom-pom.Bureau of Ordnance was well aware of the Bofors 40 mm gun. The firm York Safe and Lock was negotiating with Bofors to attain the rights to the air-cooled version of the weapon. At the same time Henry Howard, an engineer, and businessman became aware of it and contacted RADM W. R. Furlong, chief of the Bureau of Ordnance. He ordered the Bofors weapon system to be investigated. York Safe and Lock would be used as the contracting agent. The system had to be redesigned for both the English measurement system and mass production, as the original documents recommended hand fitting parts and drilling to shape.As early as 1928 the US Navy saw the need to replace the.50 caliber machine gun with something heavier. The 1.1 "/75 (28 mm) Mark 1 was designed. Placed in quadruple mounts with a 500 rpm rate of fire it would have fit the requirements. However, the gun was suffering teething issues being prone to jamming. While this could have been solved the weight of the system was equal to that of the quad-mount Bofors 40 mm while lacking the range and power that the Bofors provided. The gun was relegated to smaller less vital ships by the end of the war.The5 "/38 naval gunrounded out the US Navy's AA suite. A dual purpose mount, it was used in both the surface and AA roles with great success.

Mated with the Mark 37 director and the proximity fuse it could routinely knock drones out of the sky at ranges as far as 13,000 yards.

5-inch,40 mmand20 mmfire directed fromUSSNew Mexicoat aKamikaze,Battle of Okinawa,1945

A 3 "/50 MK 22 semiautomatic dual gun was produced but not employed before the end of the war and therefore beyond the scope of this article. However early marks of the 3" /50 were employed in destroyer escorts and on merchant ships. 3″/50caliberguns (Marks 10, 17, 18, and 20) first entered service in 1915 as a refit toUSSTexas(BB-35),and were subsequently mounted on many types of ships as the need for anti-aircraft protection was recognized. During World War II, they were the primary gun armament ondestroyer escorts,patrol frigates,submarine chasers,minesweepers,some fleetsubmarines,and other auxiliary vessels, and were used as a secondary dual-purpose battery on some other types of ships, including some older battleships. They also replaced the original low-angle4 "/50 caliber guns(Mark 9) on "flush-deck"WickesandClemson-class destroyersto provide better anti-aircraft protection. The gun was also used on specialist destroyer conversions; the "AVD"seaplane tenderconversions received two guns; the "APD"high-speed transports,"DM"minelayers,and"DMS" minesweeperconversions received three guns, and those retaining destroyer classification received six.

One of eightflak towersbuilt duringWorld War IIinVienna

A British North Sea World War IIMaunsell Fort

The Germans developed massive reinforced-concreteblockhouses,some more than six stories high, which were known asHochbunker'high bunkers' or "Flaktürme"flak towers,on which they placed anti-aircraft artillery. Those in cities attacked by the Allied land forces became fortresses. Several inBerlinwere some of the last buildings to fall to the Soviets during theBattle of Berlinin 1945. The British built structures such as theMaunsell Fortsin theNorth Sea,theThames Estuaryand other tidal areas upon which they based guns. After the war most were left to rot. Some were outside territorial waters, and had a second life in the 1960s as platforms forpirate radiostations, while another became the base of amicronation,thePrincipality of Sealand.

A USAAFB-24bomber emerges from a cloud of flak with its No. 2 engine smoking.

Some nations started rocket research before World War II, including for anti-aircraft use. Further research started during the war. The first step was unguided missile systems like the British2-inch RPand 3-inch, which was fired in large numbers fromZ batteries,and were also fitted to warships. The firing of one of these devices during an air raid is suspected to have caused theBethnal Green disasterin 1943.Facing the threat of JapaneseKamikazeattacks the British and US developed surface-to-air rockets like BritishFairey Stoogeor the AmericanLarkas counter measures, but none of them were ready at the end of the war. The Germans missile research was the most advanced of the war as the Germans put considerable effort in the research and development of rocket systems for all purposes. Among them were severalguided and unguided systems.Unguided systems involved theFliegerfaust(literally "aircraft fist" ) rocket launcher as the firstMANPADS.Guided systems were several sophisticated radio, wire, or radar guided missiles like theWasserfall('waterfall') rocket. Owing to the severe war situation for Germany all of those systems were only produced in small numbers and most of them were only used by training or trial units.

Flak in the Balkans, 1942(drawing byHelmuth Ellgaard)

Another aspect of anti-aircraft defence was the use ofbarrage balloonsto act as physical obstacle initially to bomber aircraft over cities and later for ground attack aircraft over theNormandy invasionfleets. The balloon, a simple blimp tethered to the ground, worked in two ways. Firstly, it and the steel cable were a danger to any aircraft that tried to fly among them. Secondly, to avoid the balloons, bombers had to fly at a higher altitude, which was more favourable for the guns. Barrage balloons were limited in application, and had minimal success at bringing down aircraft, being largely immobile and passive defences.

The Allies' most advanced technologies were showcased by the anti-aircraft defence against the GermanV-1cruise missiles (V stands forVergeltungswaffe,'retaliation weapon'). The 419th and 601st anti-aircraft gun battalions of the US Army were first allocated to the Folkestone-Dover coast to defend London, and then moved to Belgium to become part of the "Antwerp X" project coordinated from theLe Grand VeneurinKeerbergen.With the liberation of Antwerp, the port city immediately became the highest priority target, and received the largest number of V-1 and V-2 missiles of any city. The smallest tactical unit of the operation was a gun battery consisting of four 90 mm guns firing shells equipped with a radioproximity fuse.Incoming targets were acquired and automatically tracked bySCR-584 radar,. Output from the gun-laying radar was fed to theM9 gun director,an electronic analogue computer to calculate the lead and elevation corrections for the guns. With the help of these three technologies, close to 90% of the V-1 missiles, on track to the defence zone around the port, were destroyed.

Post-war

A 1970s-eraTalosanti-aircraft missile, fired from acruiser

Post-war analysis demonstrated that even with newest anti-aircraft systems employed by both sides, the vast majority of bombers reached their targets successfully, on the order of 90%. While these figures were undesirable during the war, the advent of thenuclear bombconsiderably altered the acceptability of even a single bomber reaching its target.

The developments during World War II continued for a short time into the post-war period as well. In particular the US Army set up a huge air defence network around its larger cities based on radar-guided 90 mm and 120 mm guns. US efforts continued into the 1950s with the 75 mmSkysweepersystem, an almost fully automated system including the radar, computers, power, and auto-loading gun on a single powered platform. The Skysweeper replaced all smaller guns then in use in the Army, notably the 40 mm Bofors. By 1955, the US military deemed the 40 mm Bofors obsolete due to its reduced capability to shoot down jet powered aircraft, and turned to SAM development, with theNike Ajaxand theRSD-58.In Europe NATO's Allied Command Europe developed an integrated air defence system, NATO Air Defence Ground Environment (NADGE), that later became theNATO Integrated Air Defence System.

The introduction of the guided missile resulted in a significant shift in anti-aircraft strategy. Although Germany had been desperate to introduce anti-aircraft missile systems, none became operational during World War II. Following several years of post-war development, however, these systems began to mature into viable weapons. The US started an upgrade of their defences using the Nike Ajax missile, and soon the larger anti-aircraft guns disappeared. The same thing occurred in theUSSRafter the introduction of theirSA-2 Guidelinesystems.

A three-personJASDFfireteam practices using a rocket target with a training variant of aType 91 KaiMANPADSduring an exercise atEielson Air Force Base,Alaska, as part of Red Flag – Alaska

As this process continued, the missile found itself being used for more and more of the roles formerly filled by guns. First to go were the large weapons, replaced by equally large missile systems of much higher performance. Smaller missiles soon followed, eventually becoming small enough to be mounted on armoured cars and tank chassis. These started replacing, or at least supplanting, similar gun-basedSPAAGsystems in the 1960s, and by the 1990s had replaced almost all such systems in modern armies. Man-portable missiles, MANPADS, as they are known today, were introduced in the 1960s and have supplanted or replaced even the smallest guns in most advanced armies.

In the 1982Falklands War,the Argentine armed forces deployed the newest west European weapons including the 35 mmOerlikon GDF-002 twin cannonandRoland missile.TheRapiermissile system was the primary GBAD system, used by both British artillery and RAF regiment, a few brand-newFIM-92 Stingerwere used by British special forces. Both sides also used theBlowpipe missile.British naval missiles used includedSea Dartand the olderSea Sluglonger range systems,SeaCatand the newSea Wolfshort range systems. Machine guns in AA mountings were used both ashore and afloat.

During the2008 South Ossetia warair power faced off against powerful SAM systems, like the 1980sBuk-M1.

In February 2018, an Israeli F-16 fighter was downed in the occupiedGolan Heightsprovince, after it had attacked an Iranian target in Syria.In 2006, Israel also lost a helicopter over Lebanon, shot down by a Hezbollah rocket.

AA warfare systems

AGepardin motion at the 2015 Military Day inUffenheim.The Gepard is an autonomous all-weather-capable Germanself-propelled anti-aircraft gunsystem armed with twinOerlikon GDF.

Bangladesh ArmyCS/AA3 35 mm twin anti-aircraft gun system along with its FW-2fire control radarsystem behind. CS/AA3 is a Chinese variant of the Oerlikon GDF.

Although the firearms used by the infantry, particularly machine guns, can be used to engage low altitude air targets, on occasion with notable success, their effectiveness is generally limited and the muzzle flashes reveal infantry positions. Speed and altitude of modern jet aircraft limit target opportunities, and critical systems may be armoured in aircraft designed for theground attack role.Adaptations of the standardautocannon,originally intended for air-to-ground use, and heavierartillerysystems were commonly used for most anti-aircraft gunnery, starting with standard pieces on new mountings, and evolving to specially designed guns with much higher performance prior to World War II.

Theshellsfired by these weapons are usually fitted with different types offuses(barometric,time-delay, orproximity) to explode close to the airborne target, releasing a shower of fast metal fragments. For shorter-range work, a lighter weapon with a higherrate of fireis required, to increase a hit probability on a fast airborne target. Weapons between20 mmand 40 mm calibre have been widely used in this role. Smaller weapons, typically.50 calibre or even 8 mm rifle calibre guns have been used in the smallest mounts.

Unlike the heavier guns, these smaller weapons are in widespread use due to their low cost and ability to quickly follow the target. Classic examples of autocannons and large calibre guns are the40 mm autocannon from Boforsand the8.8 cm FlaK 18, 36 gundesigned by Krupp. Artillery weapons of this sort have for the most part been superseded by the effective surface-to-air missile systems that were introduced in the 1950s, although they were still retained by many nations. The development of surface-to-air missiles began inNazi Germanyduring the late World War II with missiles such as theWasserfall,though no working system was deployed before the war's end, and represented new attempts to increase effectiveness of theanti-aircraft systemsfaced with growing threat frombombers.Land-based SAMs can be deployed from fixed installations or mobile launchers, either wheeled or tracked. The tracked vehicles are usually armoured vehicles specifically designed to carry SAMs.

Larger SAMs may be deployed in fixed launchers, but can be towed/re-deployed at will. The SAMs launched by individuals are known in the United States as the Man-Portable Air Defence Systems (MANPADS). MANPADS of the former Soviet Union have been exported around the World, and can be found in use by many armed forces. Targets for non-ManPAD SAMs will usually be acquired by air-searchradar,then tracked before/while a SAM is "locked-on" and then fired. Potential targets, if they are military aircraft, will beidentified as friend or foebefore being engaged. The developments in the latest and relatively cheap short-range missiles have begun to replace autocannons in this role.

Soviet85mmanti-aircraft guns deployed in the neighborhood ofSt Isaac's Cathedralduring theSiege of Leningrad(formerly Petrograd, now called St. Petersburg) in 1941.

The interceptor aircraft (or simply interceptor) is a type offighter aircraftdesigned specifically to intercept and destroy enemy aircraft, particularlybombers,usually relying on high speed andaltitudecapabilities. A number of jet interceptors such as theF-102 Delta Dagger,theF-106 Delta Dart,and theMiG-25were built in the period starting after the end of World War II and ending in the late 1960s, when they became less important due to the shifting of thestrategic bombingrole toICBMs.Invariably the type is differentiated from other fighter aircraft designs by higher speeds and shorter operating ranges, as well as much reduced ordnance payloads.

Theradarsystems useelectromagneticwaves to identify the range, altitude, direction, or speed of aircraft andweather formationsto provide tactical and operational warning and direction, primarily during defensive operations. In their functional roles they provide target search, threat detection,guidance,reconnaissance,navigation,instrumentation,andweather reportingsupport to combat operations.

Anti-UAV defences

See also:Unmanned aerial vehicle § Counter unmanned air system

Ananti-UAV defence system(AUDS) is a system for defence against militaryunmanned aerial vehicles.A variety of designs have been developed, using lasers,net-guns and air-to-air netting, signal jamming, and hi-jacking by means of in-flight hacking.Anti-UAV defence systems have been deployed againstISILdrones during theBattle of Mosul (2016–2017).

Alternative approaches for dealing with UAVs have included using ashotgunat close range, and for smaller drones, training eagles to snatch them from the air.This only works on relatively small UAVs andloitering munitions(also called "suicide drones" ). Larger UCAVs such as theMQ-1 Predatorcan be (and frequently are) shot down like manned aircraft of similar sizes and flight profiles.

TheRoyal Navy'sType 45 destroyersare advanced air defence ships

Future developments

Guns are being increasingly pushed into specialist roles, such as the DutchGoalkeeper CIWS,which uses theGAU-8 Avenger30 mm seven-barrelGatling gunfor last ditch anti-missile and anti-aircraft defence. Even this formerly front-line weapon is currently being replaced by new missile systems, such as theRIM-116 Rolling Airframe Missile,which is smaller, faster, and allows for mid-flight course correction (guidance) to ensure a hit. To bridge the gap between guns and missiles, Russia in particular produces theKashtan CIWS,which uses both guns and missiles for final defence with two six-barrelled 30 mmGsh-6-30rotary canon and eight9M311surface-to-air missiles provide for its defensive capabilities.

Upsetting this development to all-missile systems is the current move tostealth aircraft.Long range missiles depend on long-range detection to provide significant lead. Stealth designs cut detection ranges so much that the aircraft is often never even seen, and when it is, it is often too late for an intercept. Systems for detection and tracking of stealthy aircraft are a major problem for anti-aircraft development.

However, asstealth technologygrows, so does anti-stealth technology. Multiple transmitter radars such as those frombistatic radarsandlow-frequency radarsare said to have the capabilities to detect stealth aircraft. Advanced forms ofthermographic camerassuch as those that incorporateQWIPswould be able to optically see a stealth aircraft regardless of the aircraft'sradar cross-section(RCS). In addition, side-looking radars, high-poweredopticalsatellites,and sky-scanning, high-aperture,high sensitivityradarssuch asradio telescopes,would all be able to narrow down the location of a stealth aircraft under certain parameters.The newest SAMs have a claimed ability to be able to detect and engage stealth targets, with the most notable being the RussianS-400,which is claimed to be able to detect a target with a 0.05-square metre RCS from 90 km away.

Another potential weapon system for anti-aircraft use is thelaser.Although air planners have imagined lasers in combat since the late 1960s, only the most modern laser systems are currently reaching what could be considered "experimental usefulness". In particular theTactical High Energy Lasercan be used in the anti-aircraft and anti-missile role. TheALKAdirected-energy weapon(DEW) system is a Turkish dual electromagnetic/laser weapon developed byRoketsanallegedly used to destroy one ofGNC'sWing Loong IIUAVs;if true, this would represent the first known time a vehicle mounted combat laser was used to destroy another combat vehicle during genuine wartime conditions.

The future of projectile based weapons may be found in therailgun.Currently tests are underway on developing systems that could create as much damage as aTomahawk,but at a fraction of the cost. In February 2008 theUS Navytested a railgun; it fired a shell at 5,600 miles (9,000 km) per hour using 10 megajoules of energy. Its expected performance is over 13,000 miles (21,000 km) per hour muzzle velocity, accurate enough to hit a 5-metre target from 200 nautical miles (370 km) away while shooting at 10 shots per minute. It is expected to be ready in 2020 to 2025.These systems, while currently designed for static targets, would only need the ability to be retargeted to become the next generation of AA system.

Force structures

See also:Category:Air defence forces

Most Western and Commonwealth militaries integrate air defence purely with the traditional services of the military (i.e.army,navyandair force), as aseparate armor as part of artillery. In theBritish Armyfor instance, air defence is part of the artillery arm, while in thePakistan Army,it was split off from the artillery to form a separate arm of its own in 1990. This is in contrast to some (largely communist or ex-communist) countries where not only are there provisions for air defence in the army, navy and air force but there are specific branches that deal only with the air defence of territory, for example, the SovietPVO Strany.TheUSSRalso had a separate strategic rocket force in charge ofnuclearintercontinental ballistic missiles.

Navy

Soviet/RussianAK-630CIWS (close-in weapon system)

Model of the multiroleIDAS missileof theGerman Navy,which can be fired from submerged anti-aircraft weapon systems

Smaller boats and ships typically have machine-guns or fast cannons, which can often be deadly to low-flying aircraft if linked to aradar-directedfire-control systemradar-controlled cannonfor point defence. Some vessels likeAegis-equipped destroyers and cruisers are as much a threat to aircraft as any land-based air defence system. In general, naval vessels should be treated with respect by aircraft, however the reverse is equally true.Carrier battle groupsare especially well defended, as not only do they typically consist of many vessels with heavy air defence armament but they are also able to launchfighter jetsforcombat air patroloverhead to intercept incoming airborne threats.

Nations such as Japan use their SAM-equipped vessels to create an outer air defence perimeter andradar picketin the defence of its Home islands, and the United States also uses its Aegis-equipped ships as part of itsAegis Ballistic Missile Defense Systemin the defence of the Continental United States.

Some modern submarines, such as theType 212 submarinesof theGerman Navy,are equipped with surface-to-air missile systems, since helicopters andanti-submarine warfareaircraft are significant threats. The subsurface launched anti-air missile was first purposed by US Navy Rear Admiral Charles B. Momsen, in a 1953 article.

Layered air defence

ARIM-67surface to air missile intercepts aFirebeedrone atWhite Sands,1980.

Layered air defence in naval tactics, especially within a carrier group, is often built around a system of concentric layers with the aircraft carrier at the centre. The outer layer will usually be provided by the carrier's aircraft, specifically itsAEW&Caircraft combined with theCAP.If an attacker is able to penetrate this layer, then the next layers would come from thesurface-to-air missilescarried by the carrier's escorts; the area-defence missiles, such as theRIM-67 Standard,with a range of up to 100 nmi, and the point-defence missiles, like theRIM-162 ESSM,with a range of up to 30 nmi. Finally, virtually every modern warship will be fitted with small-calibre guns, including aCIWS,which is usually a radar-controlledGatling gunof between 20 mm and 30 mm calibre capable of firing several thousand rounds per minute.

Army

Armies typically have air defence in depth, from integralman-portable air-defense systems(MANPADS) such as theRBS 70,StingerandIglaat smaller force levels up to army-level missile defence systems such asAngaraandPatriot.Often, the high-altitude long-range missile systems force aircraft to fly at low level, where anti-aircraft guns can bring them down. As well as the small and large systems, for effective air defence there must be intermediate systems. These may be deployed at regiment-level and consist of platoons of self-propelled anti-aircraft platforms, whether they areself-propelled anti-aircraft guns(SPAAGs), integrated air-defence systems like2K22 Tunguskaor all-in-one surface-to-air missile platforms likeRolandorSA-8 Gecko.

On a national level the United States Army was atypical in that it was primarily responsible for the missile air defences of the Continental United States with systems such asProject Nike.

Air force

A USAFF-22A Raptorfiring anAIM-120air to air missile

Air defence by air forces is typically provided byfighter jetscarryingair-to-air missiles.However, most air forces choose to augment airbase defence with surface-to-air missile systems as they are such valuable targets and subject to attack by enemy aircraft. In addition, some countries choose to put all air defence responsibilities under the air force.

Area air defence

Area air defence, the air defence of a specific area or location, (as opposed topoint defence), have historically been operated by both armies (Anti-Aircraft Commandin the British Army, for instance) and Air Forces (theUnited States Air Force'sCIM-10 Bomarc). Area defence systems have medium to long range and can be made up of various other systems and networked into an area defence system (in which case it may be made up of several short range systems combined to effectively cover an area). An example of area defence is the defence of Saudi Arabia and Israel byMIM-104 Patriotmissile batteries during the firstGulf War,where the objective was to cover populated areas.

Tactics

Mobility

The RussianPantsir-S1can engage targets while moving, thus achieving high survivability.

Most modern air defence systems are fairly mobile. Even the larger systems tend to be mounted on trailers and are designed to be fairly quickly broken down or set up. In the past, this was not always the case. Early missile systems were cumbersome and required much infrastructure; many could not be moved at all. With the diversification of air defence there has been much more emphasis on mobility. Most modern systems are usually either self-propelled (i.e. guns or missiles are mounted on a truck or tracked chassis) or towed. Even systems that consist of many components (transporter/erector/launchers,radars,command posts etc.) benefit from being mounted on a fleet of vehicles. In general, a fixed system can be identified, attacked and destroyed whereas a mobile system can show up in places where it is not expected. Soviet systems especially concentrate on mobility, after the lessons learnt in theVietnam warbetween the US and Vietnam with theSA-2 Guideline.

Air defence versus air defence suppression

AGM-88 HARMunder the fuselage ofn aLuftwaffePanavia Tornado

Many nations have developed significant tactics forair defence suppression.Dedicated weapons such asanti-radiation missilesand advancedelectronics intelligenceandelectronic countermeasuresplatforms seek to suppress or negate the effectiveness of an opposing air-defence system. It is an arms race; as better jamming, countermeasures and anti-radiation weapons are developed, so are better SAM systems withECCMcapabilities and the ability to shoot down anti-radiation missiles and other munitions aimed at them or the targets they are defending.

Insurgent tactics

Stinger missilessupplied by the United States were used against the aircraft of the Soviet Union by theAfghanmujahideenduring the Soviet occupation of Afghanistan in the Cold War.Rocket-propelled grenades(RPGs) can be—and often are—used against hovering helicopters (e.g., by Somali militiamen during the1993 Battle of Mogadishu.Firing an RPG at steep angles poses a danger to the user, because the backblast from firing reflects off the ground. In Somalia, militia members sometimes welded a steel plate onto the exhaust end of an RPG's tube to deflect pressure away from the shooter when shooting up at US helicopters.RPGs are used in this role only when more effective weapons are not available.

Another example of using RPGs against helicopters isOperation Anacondain March 2002 in Afghanistan. Taliban insurgents defendingShah-i-Kot Valleyused RPGs in a direct fire role against landing helicopters. Four rangers were killedwhen their helicopter was shot down by an RPG, and SEAL team member Neil C. Roberts fell out of his helicopter when it was hit by two RPGs.In other instances helicopters have been shot down in Afghanistan during a missionin Wardak province. One feature that makes RPGs useful in air defence is that they are fused to automatically detonate at 920 m.If aimed into the air this causes the warhead to airburst which can release a limited but potentially damaging amount of shrapnel hitting a helicopter landing or taking off.

For insurgents the most effective method ofcountering aircraftis to attempt to destroy them on the ground, either by penetrating an airbase perimeter and destroying aircraft individually, e.g. theSeptember 2012 Camp Bastion raid,or finding a position where aircraft can be engaged with indirect fire, such as mortars. A recent trend emerging during theSyrian Civil Waris the use ofATGMagainst landing helicopters.

See also

• Air defence forces
• Air supremacy
• Gun laying
• List of anti-aircraft weapons
• Self-propelled anti-aircraft weapon
• The bomber will always get through

References

Sources

• AAP-6 NATO Glossary of Terms. 2009.
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• Friedman, Norman (2014).Naval Anti-Aircraft Guns & Gunnery.Seaforth.ISBN9781473852846.
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• Hogg, Ian V.(1997).German Artillery of World War Two.London:Greenhill Books.ISBN1-85367-261-0.
• Routledge, Brigadier NW. (1994).History of the Royal regiment of Artillery – Anti-Aircraft Artillery 1914–55.London: Brassey's.ISBN1-85753-099-3.
• Handbook for the Ordnance, Q.F. 3.7-inch Mark II on Mounting, 3.7-inch A.A. Mark II – Land Service. 1940. London: War Office 26|Manuals|2494
• History of the Ministry of Munitions. 1922. Volume X The Supply of Munitions, Part VI Anti-Aircraft Supplies. Reprinted by Naval & Military Press Ltd and Imperial War Museum.
• Flavia Foradini:I bunker di Vienna ", Abitare 2/2006, Milano
• Flavia Foradini, Edoardo Conte:I templi incompiuti di Hitler ", catalogo della mostra omonima, Milano, Spazio Guicciardini, 17.2-13.3.2009

External links

• "Flak (1943)"onYouTube
• 1914 1918 war in Alsace – The Battle of Linge 1915 – The 63rd Anti Aircraft Regiment in 14 18 – The 96th poste semi-fixed in the Vosges
• Archie to SAM: A Short Operational History of Ground-Based Air Defenseby Kenneth P. Werrell (book available for download)
• Japanese Anti-aircraft land/vessel doctrines in 1943–44
• 2nd/3rd Australian Light Anti-Aircraft Regiment