Anti-aircraft, or air defense, is any method of combating military aircraft from the ground. Various guns and cannons have been used in this role since the first military aircraft were used in World War I, growing in power and accuracy over the years. Starting in the post-World War II era the guns were joined by the guided missile, specifically the"surface-to-air missile", and today both are used in combination in most roles.
Adaptations of standard artillery systems were commonly used for most long-range anti-aircraft artillery, starting with standard pieces on new mountings, and evolving to custom guns with much higher performance prior to World War II. Their shells are usually fitted with different types of fuses (barometric (air pressure), time-delay, or proximity) to send exploding "flak" into a specified area. The classic example of a large, long-range anti-aircraft gun is the German 88 mm gun. Long range weapons of this sort were replaced outright with the introduction of missile systems in the 1950s.
For shorter-range work a lighter weapon with a higher rate of fire is required, to guarantee a hit on a quickly traversing target. Weapons of 20 mm, 37 mm and 40 mm have been widely used in this role. Unlike the heavier guns, these smaller weapons are still in widespread use today for the same reasons as they were originally introduced, that missile systems cannot traverse or react fast enough to targets that are manuvering close to the ground. Modern systems often use weapons originally intended for air-to-ground use, and are known as autocannon. The very latest of short-range missiles appear to be able to replace guns even in this role.
Nicknames for anti-aircraft guns include AAA or triple-A for anti-aircraft artillery, ack-ack (from the World War I phonetic alphabet for AA), archie (a WWI British term believed to derive via the Royal Flying Corps from the music-hall comedian George Robey's line "Archibald, certainly not!"), and flak (from the German Flugzeugabwehrkanone, aircraft defense cannon). An anti_aircraft missile is a ground_based missile used to destroy aircraft.
The U.S. Navy uses the acronym AAW to stand for anti-air warfare; most groups of ships will have a designated AAW commander among them. In the Russian Army, Air Defense is a separate armed service, reflecting its extreme importance in Russian doctrine. The United States Army has disdained air defense for ground units, counting on achieving air superiority. This has left a gap in American military equipment between the man-portable Stinger and the theater anti-missile system Patriot.
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, French troops outside the city started an attempt at resupply via balloon. Germany that development of anti-aircraft guns continued. In 1909 a number of Krupp's designs were shown, including adaptations of their 65 mm 9-pounder, a 75 mm 12-pounder, and even a 105 mm gun. By the start of World War I the 75 mm had become the standard German weapon, and came mounted on a large traverse that could be easily picked up on a wagon for movement.
Other countries involved seem to have largely ignored the possibility of aircraft being an important part of the hostilities, but this soon changed when German spotter aircraft started calling down increasingly accurate Russian 76.2 mm, typically simply propped up on some sort of embankment to get the muzzle pointed skyward. The British Army decided on an entirely new weapon, and deployed a 3 inch (76 mm) gun that was perhaps the best of the bunch.
In general these ad-hoc solutions proved largely useless. With little experience in the role, and no ability to spot the "fall" of their rounds with accuracy, gunners proved unable to get the altitude correct and most rounds fell well below their targets. The exception to this rule were the guns protecting spotting balloons, in which case the altitude could be accurately measured from the length of the cable holding the balloon. The Krupp guns were later supplied with an optical sighting system and soon improved their capabilities, but these sorts of systems were not deployed by other forces.
As aircraft started to be used in tactical roles against ground targets, these larger weapons proved too ponderous to aim at the quickly moving targets. Soon the forces were adding various machine gun based weapons mounted on poles, and the British also introduced another new weapon based on their 1-pounder "pom-pom" (a 20 mm belt-fed gun). These short-range weapons proved more deadly, and the Red Baron arguably fell victim to an anti-aircraft Vickers gun.
When the war ended it was clear that the increasing capabilities of aircraft would require a much more serious attempt at downing them. Nevertheless the die was cast: anti-aircraft weapons would be based around heavy weapons attacking high-altitude targets, and on lighter weapons for use when they came to lower altitudes.
World War II
World War I had proven that the aircraft was an important part of the battlefield, even if used solely in the reconnaissance role. As the capabilities of aircraft improved, and more specificially their engines, it was clear that their role in future combat would be even more critical as their warload grew. Many felt that the higher speeds and altitudes would render anti-aircraft systems useless, and little effort was put into improving systems.
So once again only Germany that seriously considered what to do about this. They developed a number of new anti-aircraft weapons in the late 1920s and early 1930s, often in collaboration with Swiss and Swedish companies, including a new rapid-fire 20 mm gun for low-altitude work, and a 37 mm gun for low and medium altitudes. By the mid-1930s the 20 mm was considered to be too low power against the increasingly fast planes, but instead of introducing a new gun, Krupps managed to squeeze four of the existing 20 mm guns onto a single carriage of about the same weight. By the end of the war Germany had essentially given up on the 20 mm as lacking punch. It was never cleanly replaced however; the 37 mm was available in limited numbers, and a new dual-30 mm system based on the MK 103 aircraft gun was never put into widespread use.
Their high-altitude needs were originally going to be filled by a 75 mm gun from Krupp, designed in collaborated with their Swedish counterpart Bofors, but the specifications were later amended to require much higher performance. In response Krupp's engineers presented a new 88 mm gun design, the Flak 18. The eighty-eight would go on to become one of the most famous Spain during the Spanish Civil War, the gun proved to be one of the best anti-aircraft guns in the world, as well as particularly deadly against tanks. It is in this later role that it became most widely known, the bane of allied tank crews everywhere.
After the Dambusters raid in 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 centralized control system including both search and targeting radar, which calculated the aim point for the guns after considering windage and ballisitics, the commands were then sent to the guns which used hydraulics to 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.
In the late 1920s the Swedish Navy had ordered the development of a 40 mm naval anti-aircraft gun from the Bofors company. The new gun proved to be light, fast and reliable, and a mobile version on a four wheel carriage was soon developed. Known simply as the 40 mm, it was adopted by some 17 different nations just before WWII.
At the start of the war Britain had started a slow upgrade to their own systems, including a new 90 mm gun in addition to their existing WWI-era 3" guns. Both were delivered with optical sighting systems for ranging. At the small-end of the scale a number of 20 mm designs were used, but testing showed, as Germany had discovered, that these weapons were of little use against modern aircraft.
Their solution was the introduction into service of the 40 mm Bofors gun. 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, in order to make workers on the assembly line work harder. The drawings were also handed over to the Americans who illegally copied the 40 mm gun during the war.
Service trials demonstrated another problem however, that the problem of ranging and tracking the new high-speed targets was almost impossible – at shorter ranges the "lead" required (aiming in front of the target because it is moving) is so small that it can be done manually, and at very long ranges the apparent speed is so slow that existing manual calculators were good enough. For the ranges and speeds that the Bofors worked at neither solution was good enough.
The solution was automation, in the form of a mechanical computer, the Kerrison 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 which incorporated radar for ranging, and then tracking.
Although they receive little attention, US Army anti-aircraft systems were actually quite good. Their smaller tactical needs were filled with quad-mounted 50 calibre (12.7 mm) machine guns, which were often mounted on the back of a half-track to form the Half Track M16, Anti-Aircraft. Although of even less power than Germany's 20 mm systems, they were at least widely available. Their larger 90 mm heavy guns would 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. Finally just as the war was ending a new 120 mm gun with an impressive 60,000 ft altitude capability was introduced, the so-called stratosphere gun, which would continue in use after the war into the 1950s.
The Germans developed massive reinforced concrete blockhouses, some more than six stories high, which known as Hochbunker "High Bunkers" or "Flakturm" Flak Towers, on which they placed Anti-aircraft Artillery. Those which were in cities attacked by the Allied land forces became fortresses. Several in Berlin were some of the last buildings to fall to the Soviets during the Battle of Berlin in 1945. The British built structures in the Thames estuary and other tidal areas on which they based Triple A. After the war most were left to rot. Some were outside territorial waters, and had a second life in the 1960s as a platforms for Pirate radio stations.
Post-war analysis demonstrated that even with newer anti-aircraft systems employed by both sides, the vast majority of bombers reached their targets successfully, on the order of 90%. This was bad enough during the war, but the introduction of the nuclear bomb into the equation upset things considerably. Now even a single bomber reaching the target would be generally unacceptable.
The developments during WWII continued for a short time into the post-war period as well. In particular the US Army set up a huge air defense network around its larger cities based on radar-guided 90 mm and 120 mm guns. But given the general lack of success of guns against even propeller bombers, it was clear that any defense was going to have to rely almost entirely on interceptor aircraft. Despite this US efforts continued into the 1950s with the 75 mm Skysweeper system.
Things changed with the introduction of the guided missile. Although Germany had been desperate to introduce them during the war, none were ready for service, and British countermeasures were likely to defeat them even if they were. With a few years of development however, these system started to mature into practical weapons. The US started an upgrade of their defenses using the Nike Ajax missile, and soon the larger anti-aircraft guns disappeared. The same thing occurred in the USSR after the introduction of their SA-2 Guideline systems.
The evolution since this time has been a slow change from guns to missiles for the shorter range roles. Originally missiles were useful only as a replacement for the very largest of anti-aircraft guns, but by the 1960s they had been scaled down to the point where they were also replacing smaller weapons previously serviced by guns in the 40 mm to 57 mm range. Today man_portable missiles, known as MANPADS, are replacing even the very smallest of gun systems.
If current trends continue, missiles will replace gun systems completely in "first line" service. Guns are being increasingly pushed into specialist roles, such as the US Phalanx CIWS which uses a 20 mm M61 Vulcan gun firing at over 4,500 rounds per minute for last ditch anti-missile and anti-aircraft fighting. Even this formerly first-rate weapon is currently being replaced by a new missile system, the Rolling Airframe Missile, which is smaller, faster, and allows for mid-flight course correction (guidance) to ensure a hit.
Upsetting this development to all-missile systems is the current move to stealth_based aircraft. Long range missiles depend on long_range detection in order to provide significant lead. Stealth designs cut detection ranges so much that the aircraft is often never even seen, and when it is, often too late for an intecept. Systems for detection and tracking of stealthy aircraft are a major problem for anti_aircraft development.
Another potential weapon system for anti_aircraft use is the laser. Although originally intended to be used in this role since the late 1960s, the most modern laser systems are currently reaching what could be considered "experimental usefulness". In particular the HEL can be used in the anti-aircraft and anti-missile role. If current developments continue, it is reasonable to suggest that lasers will play a major role in air defense starting in the next 10 years.
List of Anti-Aircraft Weapons
- M-163 Hovet
- M-163 Machbet (armed with M61 Vulcan and FIM-92 Stinger)
- Scotti 20/L77
- Breda M1935 20/L53
- M1941 90/L53
- NASAMS (using AMRAAM missiles)
- SA-1 Guild
- SA-2 Guideline
- SA-3 Goa
- SA-4 Ganef
- SA-5 Gammon
- SA-6 Gainful
- SA-7 Grail
- SA-8 Gecko
- SA-9 Gaskin
- SA-10 Grumble
- SA-11 Gadfly
- SA-12 Gladiator/Giant
- SA-13 Gopher
- SA-14 Gremlin
- SA-15 Gauntlet
- SA-16 Gimlet
- SA-17 Grizzly
- SA-18 Grouse
- SA-19 Grisom
- SA-20 Gargoyle
- SA-X-21 "Triumf"
- M-163 SPAA
- MIM-104 Patriot
- FIM-92 Stinger
- Redeye Anti-aircraft Missile