Close air support

Close air support
A Boeing AH-64 Apache attack helicopter provides close air support to United States Army soldiers patrolling the Tigris River southeast of Baghdad, Iraq during the Iraq War

In military tactics, close air support (CAS) is defined as air action by fixed or rotary winged aircraft against hostile targets that are close to friendly forces, and which requires detailed integration of each air mission with fire and movement of these forces.[1]

The determining factor for CAS is detailed integration, not proximity. CAS may need to be conducted far from friendly forces, if the mission requires detailed integration with the fire and movement of these forces. A closely related subset of air interdiction, battlefield air interdiction denotes interdiction against units with near-term effects on friendly units, but which does not require integration with friendly troop movements. The term "battlefield air interdiction" is not currently used in US joint doctrine.

Close air support requires excellent coordination with ground forces. In advanced modern militaries, this coordination is typically handled by specialists such as Joint Fires Observers, Joint Terminal Attack Controllers (JTAC)s, and Forward Air Controllers (FAC).



World War I

The Junkers J.I, a First World War German Ground-attack aircraft

The use of aircraft in the close air support of ground forces dates back to World War I, the first significant use of aerial units in warfare.[2] Air warfare, and indeed aviation itself, was still in its infancy - and the direct effect of rifle calibre machine guns and light bombs of World War I aircraft was very limited compared with the power of (for instance) a World War II fighter bomber, but close support aircraft still had a powerful psychological impact. The aircraft was a visible and personal enemy - unlike artillery - presenting a personal threat to enemy troops, while providing friendly forces assurance that their superiors were concerned about their situation. Most successful attacks of 1917 - 1918 included planning for co-ordination between aerial and ground units, although it was very hard at this early date to co-ordinate these attacks due to the primitive nature of air-to-ground radio communication. Though most airpower proponents sought independence from ground commanders and hence pushed the importance of interdiction and strategic bombing, they nonetheless recognised the need for close air support.[3]

The British Royal Flying Corps and the U.S. Army Air Service saw "trench strafing" as another task for ordinary pursuit or fighter aircraft, such as the Airco DH.5 and Sopwith Camel, and did not seek out specialized units or equipment until the late months of the war. The first British specialised ground attack aircraft, the Sopwith Salamander, was too late to see action. Since pilots lacked specific training, and their aircraft were both slow and fragile, they suffered heavy casualties while flying low over enemy positions. For example, No. 80 Squadron RAF averaged 75% losses for the last 10 months of the war. The Germans and French, however, developed tactics, training, and formations for ground support. Germany also built specialist aircraft, culminating in the well armoured Junkers J.I. By spring 1918, Germany had 38 Schlachtstaffeln (battle squadrons, often abbreviated to Schlasta) trained to bomb and strafe below 200 feet in support of ground forces.[3]

Inter-War period - Framing the debate

During the inter-war period, airpower advocates crystallized their views on the role of airpower in warfare. Aviators and ground officers developed largely opposing views on the importance of CAS, views that would frame institutional battles for CAS in the 20th century. The inter-war period also saw the use of CAS in a number of conflicts, principally Spain and China and the Banana Wars. Observers and participants from the major parties of World War II would base their CAS strategies on experience and observation from these conflicts.

The development of the close air support came in between the World Wars, mostly through the adaptation of fighters or light bombers. Following the end of World War I, the United States embraced its role of global power and the United States Marine Corps became the preferred force for military intervention and where the Marines went so went Marine aviation. It was while fighting bandits and insurgents in places such as Haiti, the Dominican Republic and Nicaragua that Marine Aviators would begin to experiment with air-ground tactics making the support of their fellow Marines on the ground their primary mission. It was in Haiti that U.S. Marines began to develop the tactic of dive bombing and in Nicaragua where they began to perfect it. While other nations and services had tried variations of this technique, Marine aviators were the first to embrace it and make it part of their tactical doctrine.[4]

Aviators, who wanted institutional independence from the Army, pushed for a view of airpower centered around interdiction, which would relieve them of the necessity of integrating with ground forces and allow them to operate as an independent military arm. They saw close air support as both the most difficult and most inefficient use of aerial assets. Close air support was the most difficult mission, requiring identifying and distinguishing between friendly and hostile units. At the same time, targets engaged in combat are dispersed and concealed, reducing the effectiveness of air attacks. They also argued that the CAS mission merely duplicated the abilities of artillery, whereas interdiction provided a unique capability.

Ground officers contended there was rarely sufficient artillery available, and the flexibility of aircraft would be ideal for massing firepower at critical points, while producing a greater psychological effect on friendly and hostile forces alike. Moreover, unlike massive, indiscriminate artillery strikes, small aerial bombs wouldn't render ground untrafficable, slowing attacking friendly forces.[3]

World War II

World War II marked the universal acceptance of the integration of air power into combined arms warfare as close air support. Although the German Wehrmacht led the way, all the major combatants had developed effective air-ground coordination techniques by the war's end.

Western Front

A flight of Ju 87 G-2s over the Eastern Front, winter 1943-44.

As a continental power intent on offensive operations, Germany could not ignore the need for aerial support of ground operations. Though the Luftwaffe, like its counterparts, tended to focus on strategic bombing, the Luftwaffe was unique in its willingness to commit forces to CAS. In joint exercises with Sweden in 1934, the Germans were first exposed to dive-bombing, which permitted greater accuracy while making attack aircraft more difficult to track by antiaircraft gunners. As a result, Ernst Udet, chief of the Luftwaffe's development, initiated procurement of close support dive bombers on the model of the U.S. Navy's Curtiss Helldiver, resulting in the famous Junkers Ju 87 Stuka. Experience in the Spanish Civil War lead to the creation of five ground-attack groups in 1938,[dubious ] four of which would be equipped with Stukas. The Luftwaffe matched its material acquisitions with advances in the air-ground coordination. General Wolfram von Richthofen organized a limited number of air liaison detachments that were attached to ground units of the main effort. These detachments existed to pass requests from the ground to the air, and receive reconnaissance reports, but they were not trained to guide aircraft onto targets.

These preparations did not prove fruitful in the invasion of Poland, where the Luftwaffe focused on interdiction and dedicated few assets to close air support. But the value of CAS was demonstrated at the crossing of the Meuse River during the Invasion of France in 1940. General Heinz Guderian, one of the creators of the combined-arms tactical doctrine commonly known as "blitzkrieg", believed the best way to provide cover for the crossing would be a continuous stream of ground attack aircraft on French defenders. Though few guns were hit, the attacks kept the French under cover and prevented them from manning their guns. Aided by the sirens attached to Stukas, the psychological impact was disproportional to the destructive power of close air support. In addition, the reliance on air support over artillery reduced the demand for logistical support through the Ardennes. Though there were difficulties in coordinating air support with the rapid advance, the Germans demonstrated consistently superior CAS tactics to those of the British and French defenders. Later, on the Eastern front, the Germans would devise visual ground signals to mark friendly units and to indicate direction and distance to enemy emplacements.

Despite these accomplishments, German CAS was not perfect and suffered from the same misunderstanding and interservice rivalry that plagued other nations' air arms, and friendly fire was not uncommon. For example, on the eve of the Meuse offensive, Guderian's superior cancelled his CAS plans and called for high-altitude strikes from medium bombers, which would have required halting the offensive until the air strikes were complete. Fortunately for the Germans, his order was issued too late to be implemented, and the Luftwaffe commander followed the schedule he had previously worked out with Guderian. As late as November 1941, the Luftwaffe refused to provide Erwin Rommel with an air liaison officer for the Afrika Korps, because it "would be against the best use of the air force as a whole."[3]

US Navy SBD Dauntless dropping its bomb.

The Royal Air Force (RAF) entered the war woefully unprepared to provide CAS. In 1940 during the Battle of France, the Royal Air Force and Army headquarters in France were located at separate positions, resulting in unreliable communications. After the RAF was withdrawn in May, Army officers had to telephone the War Office in London to arrange for air support. The stunning effectiveness of German air-ground coordination spurred change. On the basis of tests in Northern Ireland in August 1940, Group Captain A. H. Wann RAF and Colonel J.D. Woodall (British Army) issued the Wann-Woodall Report, recommending the creation of a distinct tactical air force and liaisons (known colloquially as "tentacles"), to accompany Army divisions and brigades. Their report spurred the RAF to create an Army Co-Operation Command and to develop tentacle equipment and procedures placing an Air Liaison Officer with each brigade.

Although the RAF was working on its CAS doctrine in London, officers in North Africa improvised their own coordination techniques. In October 1941, Sir Arthur Tedder and Arthur Coningham, senior RAF commanders in North Africa, created joint RAF-Army Air Support Control staffs at each corps and armored division headquarters, and placed a Forward Air Support Link at each brigade to forward air support requests. When trained tentacle teams arrived in 1942, they cut response time on support requests to thirty minutes.[3] It was also in the North Africa desert that the cab rank strategy was developed.[5] It used a series of three aircraft, each in turn directed by the pertinent ground control by radio. One aircraft would be attacking, another in flight to the battle area, while a third was being refuelled and rearmed at its base. If the first attack failed to destroy the tactical target, the aircraft in flight would be directed to continue the attack. The first aircraft would land for its own refuelling and rearming once the third had taken off.[citation needed]

The United States Army Air Forces (USAAF) was charged with the principal mission of strategic bombing, hence operated independently of the rest of the Army and was also initially unprepared to provide CAS. USAAF doctrinal priorities for tactical aviation were, in order, air superiority, isolation of the battlefield via supply interdiction, and thirdly, close air support. Hence during the North African Campaign CAS was poorly executed, if at all. So few aerial assets were assigned to U.S. troops that they fired on anything in the air. And in 1943, the USAAF changed their radios to a frequency incompatible with ground radios.

The situation improved during the Italian Campaign, where American and British forces, working in close cooperation, exchanged CAS techniques and ideas. There, the AAF's XII Air Support Command and the Fifth U.S. Army shared headquarters, meeting every evening to plan strikes and devising a network of liaisons and radios for communications. However, friendly fire continued to be a concern - pilots did not know recognition signals and regularly bombed friendly units, until an A-36 was shot down in self-defense by Allied tanks. The expectation of losses to friendly fire from the ground during the planned invasion of France prompted the black and white invasion stripes painted on all Allied aircraft from 1944.

In 1944, USAAF commander Lt. Gen. Henry ("Hap") Arnold acquired 2 groups of A-24 dive bombers, the army version of the Navy's SBD-2, in response to the success of the Stuka and German CAS. Later, the USAAF developed a modification of the North American P-51 Mustang with dive brakes - the North American A-36. However, there was no training to match the purchases. Though Gen. Lesley McNair, commander of Army Ground Forces, pushed to change USAAF priorities, the latter failed to provide aircraft for even major training exercises. Six months before the invasion of Normandy, 33 divisions had received no joint air-ground training.

The USAAF saw the greatest innovations in 1944 under Gen. Elwood Quesada, commander of IX Tactical Air Command, supporting the First U.S. Army. He developed the "armored column cover", where on-call fighter-bombers maintained a high-level of availability for important tank advances, allowing armor units to maintain a high tempo of exploitation even when they outran their artillery assets. He also used a modified antiaircraft radar to track friendly attack aircraft to redirect them as necessary, and experimented with assigning fighter pilots to tours as forward air controllers to familiarize them with the ground perspective. In July 1944, Quesada provided VHF aircraft radios to tank crews in Normandy. When the armored units broke out of the Normandy beachhead, tank commanders were able to communicate directly with overhead fighter-bombers. However, despite the innovation, Quesada focused his aircraft on CAS only for major offensives. Typically, both British and American attack aircraft were tasked primarily to interdiction, even though later analysis showed them to be twice as dangerous as CAS.

XIX TAC, under the command of General Otto P. Weyland utilized similar tactics to support the rapid armored advance of General Patton's Third Army in its drive across France. Armed reconnaissance was a major feature of XIX TAC close air support, as the rapid advance left Patton's Southern flank open. Such was the close nature of cooperation between the Third Army and XIX TAC that Patton actually counted on XIX TAC to guard his flanks. This close air support from XIX TAC was thus undoubtedly a key factor in the rapid advance and success of Patton's Third Army.

Soviet front

A Soviet Air Force Il-2M Sturmovik

The Red Air Force was not slow to recognize the value of ground support aircraft. Even as far back as the Battles of Khalkhyn Gol, Russian aircraft were given the task of disrupting enemy ground operations. This use increased markedly after the German invasion. Purpose-built aircraft such as the Ilyushin Il-2 Sturmovik were highly effective in blunting the activity of the Panzers. Joseph Stalin paid the Il-2 a great tribute in his own inimitable manner: when a particular production factory fell behind on its deliveries, Stalin sent the following cable to the factory manager: "They are as essential to the Red Army as air and bread".

German CAS reached its peak on the Eastern Front during the period 1941-1943. Their decline was caused by the growing strength of the Red Air Force and the redeployment of assets to defend against American and British strategic bombardment. The introduction of improved Soviet tanks, the T-34 and KV-1 temporarily reduced the effectiveness of close air support, even after the adoption of 30 mm cannon and shaped-charge bombs, until more powerful cannons, air-to-ground mortars and rockets were introduced. While German procedures for CAS led the way, their loss of air superiority and technological advantage, combined with a declining supply of aircraft and fuel, crippled their ability to provide effective CAS on the western front after 1943.

The Pacific theater

The American Navy and Marine Corps would similarly use CAS in conjunction with or as a substitute for the lack of available artillery or naval gunfire. Navy and Marine F6F Hellcats and F4U Corsairs used a variety of ordnance such as conventional bombs, rockets and napalm to disloge or attack Japanese troops utilizing cave complexes in the latter part of World War II.

Korean War

F4U-5 Corsairs provide close air support to U.S. Marines fighting Chinese forces during the war in Korea, December 1950.

From Navy experiments with the KGW-1 Loon, the Navy designation for the German V-1 flying bomb, Marine Captain Marian Cranford Dalby developed the AN-MPQ-14, a system that enabled radar-guided bomb release at night or in poor weather.[6]

Though the Marine Corps continued its tradition of intimate air-ground cooperation, the newly created Air Force again moved away from CAS, now to strategic bombers and jet interceptors. Though eventually the Air Force supplied sufficient pilots and forward air controllers to provide battlefield support, coordination was still lacking. Since pilots operated under centralized control, ground controllers were never able to familiarize themselves with pilots, and requests were not processed quickly. Harold K. Johnson, then commander of the 8th Cavalry Regiment, 1st Cavalry Division (later Army Chief of Staff) commented regarding CAS: "If you want it, you can't get it. If you can get it, it can't find you. If it can find you, it can't identify the target. If it can identify the target, it can't hit it. But if it does hit the target, it doesn't do a great deal of damage anyway."[7]

It is unsurprising, then, that MacArthur excluded USAF aircraft from the airspace over the Inchon Landing in September 1950, instead relying on Marine Aircraft Group 33 for CAS. In December 1951, Lt. Gen. James Van Fleet, commander of the Eighth U.S. Army, formally requested the United Nations Commander, Gen. Mark Clark, to permanently attach an attack squadron to each of the four army corps in Korea. Though the request was denied, Clark allocated much more Navy and Air Force aircraft to CAS. Despite the rocky start, the USAF would also work to improve its coordination efforts. It eventually required pilots to serve 80 days as forward air controllers (FACs), which gave them an understanding of the difficulties from the ground perspective and helped cooperation when they returned to the cockpit. The USAF also provided airborne FACs in critical locations. The Army also learned to assist, by suppressing anti-aircraft fire prior to air strikes.

The U.S. Army wanted a dedicated USAF presence on the battlefield to reduce fratricide, or the harm of friendly forces. The air liaison officer (ALO) was born. The ALO is an aeronautically rated officer that has spent a tour away from the cockpit, serving as the primary advisor to the ground commander on the capabilities and limitations of airpower.

Vietnam and the CAS role debate

UH-1B with rockets and minigun

During the late 1950s and early 1960s, the US Army began to identify a dedicated CAS need for itself. The Howe Board, which studied the question, published a landmark report describing the need for a helicopter-based CAS requirement.[8] However, the Army did not follow the Howze Board recommendation initially. Nevertheless it did eventually adopt the use of helicopter gunships and attack helicopters in the CAS role.[9]

AH-1 Cobra over Vietnam

Though helicopters were initially armed merely as defensive measures to support the landing and extraction of troops, their value in this role lead to the modification of early helicopters as dedicated gunship platforms. Though not as fast as fixed-wing aircraft and consequently more vulnerable to anti-aircraft weaponry, helicopters could utilize terrain for cover, and more importantly, had much greater battlefield persistence owing to their low speeds. The latter made them a natural complement to ground forces in the CAS role. In addition, newly developed anti-tank guided missiles, demonstrated to great effectiveness in the 1973 Yom Kippur War, provided aircraft with an effective ranged anti-tank weapon. These considerations motivated armies to promote the helicopter from a support role to a combat arm. Though the U.S. Army controlled rotary-wing assets, coordination continued to pose a problem. During wargames, field commanders tended to hold attack helicopters out of fear of air defenses, committing them too late to effectively support ground units. The earlier debate over control over CAS assets were reiterated between ground commanders and aviators. Nevertheless, the US Army incrementally gained increased control over its CAS role.[10]

In the mid 1970s, after Vietnam, the USAF decided to train an enlisted force to handle many of the tasks the ALO was saturated with, to include terminal attack control. Now the ALO mainly serves in the liaison role, the intricate details of mission planning and attack guidance left to the enlisted members of the Tactical Air Control Party.


An A-10 Thunderbolt II firing a AGM-65 Maverick missile.

Various aircraft can fill close air support roles. Military helicopters are often used for close air support and are so closely integrated with ground operations that in most countries they are operated by the army rather than the air force. Fighters and ground attack aircraft like the A-10 Thunderbolt II provide close air support using rockets, missiles, small bombs, and strafing runs.

In World War II, dive bombers and fighters were used in close air support. Dive bombing permitted greater accuracy than level bombing runs, while the rapid altitude change made it more difficult for antiaircraft gunners to track. The Junkers Ju 87 Stuka is the best known example of a dive bomber designed for CAS. It was fitted with wind-blown whistles on its landing gear to enhance its psychological effect.

Other than the A-36, a P-51 modified with dive brakes, the Americans and British used no dedicated CAS aircraft in World War II, preferring fighters or fighter-bombers that could be pressed into CAS service. While some such as the Hawker Typhoon and the P-47 Thunderbolt, performed admirably in that role, there were a number of compromises that prevented most fighters from making effective CAS platforms. Fighters were usually optimized for high-altitude operations without bombs or other external ordnance - flying at low level with bombs quickly expended fuel. Cannons had to be mounted differently for strafing - strafing required a further and lower convergence point than aerial combat did.

Of the World War II allies, the Soviet Union used specifically designed ground attack aircraft more than the UK and US. Such aircraft included the Ilyushin Il-2, the single most produced military aircraft design in all of aviation history.

In the Vietnam War, the United States introduced fixed and rotary wing gunships, cargo aircraft refitted as gun platforms to serve as close air support and air interdiction aircraft. The first of these was the AC-47 Spooky. Later models include the Fairchild AC-119 and the Lockheed AC-130. The AC-130 has been used extensively in Afghanistan and Iraq during recent US operations there.

A US Navy F-A-18F in a close air support configuration over Afghanistan, 29 April 2009.

Today, close support is typically carried out by fighter-bombers or dedicated ground attack aircraft, such as the A-10 Thunderbolt II Warthog or Sukhoi Su-25 Frogfoot, but even large high-altitude bombers can occasionally fill close support roles using precision guided munitions. During Operation Enduring Freedom, the lack of fighter aircraft forced military planners to rely heavily on US bombers, particularly the B-1B Lancer and B52H Stratofortress, to fill the CAS role. Bomber CAS, relying mainly on GPS guided weapons, has evolved into a devastating tactical employment methodology and has changed US doctrinal thinking regarding CAS in general. After the initial collapse of the Taliban regime in Afghanistan, airfields in Afghanistan became available for continuing operations against the Taliban and Al-Qaeda. This resulted in the majority of CAS operations being undertaken by aircraft from Belgium (F-16 Fighting Falcon), Denmark (F-16), France (Mirage 2000D), the Netherlands (F-16), Norway (F-16), the United Kingdom (Harrier GR7s,GR9s and Tornado GR4s) and the United States (A-10, AV-8B Harrier II, F-15E Strike Eagle, F/A-18 Hornet, F/A-18 Super Hornet).

Technological enhancement

The use of information technology to direct and coordinate precision air support has increased the importance of intelligence, surveillance, and reconnaissance in utilizing CAS. Laser, GPS, and battlefield data transfer are routinely used to coordinate with a wide variety of air platforms able to provide CAS. Recent doctrine[1] reflects the increased use of electronic and optical technology to direct targeted fires for CAS. Air platforms communicating with ground forces can also provide additional aerial-to-ground visual search, ground-convoy escort, and enhancement of command and control (C2), assets which can be particularly important for low intensity conflict.[11]

See also


  1. ^ a b Joint Tactics, Techniques, and Procedures for Close Air Support (2003). DoD.
  2. ^ Hallion (1990), Airpower Journal.
  3. ^ a b c d e House (2001), Combined Arms Warfare.
  4. ^ Corum & Johnson, Small Wars, p. 23-40.
  5. ^ Strike from Above: The History of Battlefield Air Attack 1911 - 1945. pp. 181–182. 
  6. ^ Krulak,First to Fight, p. 113-119
  7. ^ Blair (1987), Forgotten War, p. 577.
  8. ^ General HH Howze (Obit)
  9. ^ Transforming the Force: The 11th Air Assault Division (Test) from 1963-1965 - Page 29
  10. ^ Interservice Rivalry and Airpower in the Vietnam War - Chapter 5
  11. ^ Haun (2006), Air & Space Power Journal.


External links

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