Anti-aircraft warfare is the counter to aerial warfare[1] and includes "all measures designed to nullify or reduce the effectiveness of hostile air action".[2] 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 protect naval, ground, and air forces in any location. However, for most countries, the main effort has tended to be homeland defence. Missile defence is an extension of air defence, as are initiatives to adapt air defence to the task of intercepting any projectile in flight.
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 both autocannons and surface-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 the Second World War, the Soviet 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 with close-in weapon systems, which typically use rotary autocannons or, in very modern systems, surface-to-air adaptations of short-range air-to-air missiles, often combined in one system with rotary cannons).
It may also be called counter-air, anti-air, AA, flak, layered air defence or air defence forces.
The term air defence was probably first used by the UK when Air Defence of Great Britain (ADGB) was created as a Royal Air Force command in 1925. However, arrangements in the UK were also called "anti-aircraft", abbreviated as AA, a term that remained in general use into the 1950s. After the First World War it 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 German Flugzeugabwehrkanone), "ack-ack" (from the spelling alphabet used by the British for voice transmission of "AA");[3] and "archie" (a World War I British term probably coined by Amyas Borton, and believed to derive via the Royal Flying Corps, from the music-hall comedian George Robey's line "Archibald, certainly not!"[4]).
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".[2] In some armies the term all-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) and man-portable air-defense system (MANPADS). Anti-aircraft missiles are variously called surface-to-air missiles, ("SAMs") and surface-to-air guided weapons (SAGWs). Examples are the RIM-66 Standard, Raytheon Standard Missile 6, or the MBDA Aster missile.
Non-English terms for air defence include the German Flak or FlaK (Fliegerabwehrkanone, 'aircraft defence cannon',[5] also cited as Flugabwehrkanone), whence English flak, and the Russian term Protivovozdushnaya oborona (Cyrillic: Противовозду́шная оборо́на), a literal translation of 'anti-air defence', abbreviated as PVO.[6] In Russian, the AA systems are called zenitnye (i.e., 'pointing to zenith') systems. In French, air defence is called Défense contre les aéronefs (DCA) , aéronef meaning 'aircraft'.[7]
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".[8]
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,[9] but were quickly superseded by radar, which in turn was supplemented by optoelectronics in the 1980s. Command and control remained primitive until the late 1930s, when Britain created an integrated system[10] for ADGB that linked the ground-based air defence of the British Army's Anti-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".[2]
Rules of engagement are critical to prevent air defences engaging friendly or neutral aircraft. Their use is assisted but not governed by identification friend or foe (IFF) electronic devices originally introduced during the Second 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:
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.[11]
Ground-based air defence is deployed in several ways:
Air defence has included other elements, although after the Second World War most fell into disuse:
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".[2] 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.
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 called Voyska 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, and PVO SV, Air Defence of the Ground Forces. Subsequently, these became part of the air force and ground forces respectively.[13][14]
At the other extreme, the United States Army has an Air Defense Artillery Branch that provides ground-based air defence for both homeland and the army in the field; however, it is operationally under the Joint 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 the Royal Navy for air defence of the British Isles in World War I. However, during the Second World War, the RAF Regiment was formed to protect airfields everywhere, and this included light air defences. In the later decades of the Cold War this included the United States Air Force's operating bases in the UK. All ground-based air defence was removed from Royal Air Force (RAF) jurisdiction in 2004. The British Army's Anti-Aircraft Command was disbanded in March 1955,[15] 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, the Royal Marines also 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.[citation needed] 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 full British Army general was part of ADGB. At its peak in 1941–42 it comprised three AA corps with 12 AA divisions between them.[16]
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's Balloon Corps to be disbanded mid-war. The Confederates experimented with balloons as well.[17]
Turks carried out the first ever anti-airplane operation in history during the Italo-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.[18][19]
The earliest known use of weapons specifically made for the anti-aircraft role occurred during the Franco-Prussian War of 1870. After the disaster at Sedan, Paris was besieged and French troops outside the city started an attempt at communication via balloon. Gustav Krupp mounted a modified 1-pounder (37 mm) gun – the Ballonabwehrkanone (Balloon defence cannon) or BaK — on top of a horse-drawn carriage for the purpose of shooting down these balloons.[20][page needed]
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, Vickers Maxim, and Schneider had 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.[21]
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 the QF 3-inch and QF 4-inch AA guns and also had Vickers 1-pounder quick firing "pom-poms" that could be used in various mountings.[22][23]
The first US anti-aircraft cannon was a 1-pounder concept design by Admiral Twining in 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: the 3-inch/23 caliber gun.[24]
On the 30th of September, 1915, troops of the Serbian Army observed three enemy aircraft approaching Kragujevac. 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, private Radoje Ljutovac fired 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 the First Balkan War in 1912. This was the first occasion in military history that a military aircraft was shot down with ground-to-air artillery fire.[25][26][27]
The British recognised the need for anti-aircraft capability a few weeks before World War I broke out; on 8 July 1914, the New York Times reported 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 the Royal Naval Volunteer Reserve (RNVR) was manning AA guns and searchlights assembled from various sources at some nine ports. The Royal 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 used QF 1-pounder "pom-pom"s (37 mm versions of the Maxim Gun).[23][28]
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. The British Army adopted the 13-pounder quickly producing new mountings suitable for AA use, the 13-pdr QF 6 cwt Mk III was 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 the 13-pr QF 9 cwt and these proved much more satisfactory.[29] 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) and shrapnel were 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.[30]</
