Editing Close air support (section)

==History==

===World War I===
[[File:Royal Aircraft Factory FE2d gunner.jpg|thumb|left|The [[Royal Aircraft Factory F.E.2|F.E 2d]] was one of the first aircraft to be used for close air support in 1917 (the observer is demonstrating the use of the rear-firing [[Lewis gun]]).]]
The use of aircraft in the close air support of ground forces dates back to [[World War I]], the first conflict to make significant military use of aerial forces.<ref name="Airpower">[[#Hallion|Hallion]] (1990), ''Airpower Journal'', p. 8.</ref> Air warfare, and indeed aviation itself, was still in its infancy – and the direct effect of rifle caliber [[machine gun]]s and light bombs of World War I aircraft was very limited compared with the power of (for instance) an average [[fighter bomber]] of World War II, but CAS aircraft were still able to achieve a powerful psychological impact. Unlike [[artillery]], the aircraft was a visible and personal enemy presenting a direct threat to enemy troops, while at the same time providing friendly forces proof of support from their superiors. 

The most successful attacks of 1917–1918 had included planning for co-ordination between aerial and ground units, although it was relatively difficult at this early date to co-ordinate these attacks due to the primitive nature of air-to-ground [[radio|radio communication]]. Though most air-power proponents sought independence from ground commanders and hence pushed the importance of interdiction and strategic bombing, they nonetheless recognized the need for close air support.<ref name=House2001>[[#House|House]] (2001), ''Combined Arms Warfare''.</ref>{{page needed|date=July 2012}}

From the commencement of hostilities in 1914, aviators engaged in sporadic and spontaneous attacks on [[ground forces]], but it was not until 1916 that an air support doctrine was elaborated and dedicated [[fighter aircraft|fighters]] for the job were put into service. By that point, the startling and demoralizing effect that attack from the air could have on the troops in the [[trench]]es had been made clear.{{citation needed|date=September 2020}}

At the [[Battle of the Somme]], 18 British armed [[reconnaissance]] planes strafed the enemy trenches after conducting [[surveillance]] operations. The success of this improvised assault spurred innovation on both sides. In 1917, following the [[Second Battle of the Aisne]], the British debuted the first ground-attack aircraft, a modified [[Royal Aircraft Factory F.E.2|F.E 2b]] fighter carrying {{convert|20|lb|kg|adj=on|abbr=on}} [[bomb]]s and mounted [[machine-gun]]s. After exhausting their ammunition, the planes returned to base for refueling and rearming before returning to the battle-zone. Other modified planes used in this role were the [[Airco DH.5]] and [[Sopwith Camel]] – the latter was particularly successful in this role.<ref name="Airpower" />

Aircraft support was first integrated into a battle plan on a large scale at the 1917 [[Battle of Cambrai (1917)|Battle of Cambrai]], where a significantly larger number of [[tank]]s were deployed than previously. By that time, effective anti-aircraft tactics were being used by the enemy infantry and pilot casualties were high, although air support was later judged as having been of a critical importance in places where the infantry had got pinned down.<ref name="Hallion">{{cite book |url=https://books.google.com/books?id=ZAdtAIMTReEC |title=Strike From the Sky: The History of Battlefield Air Attack, 1910–1945 |last=Hallion |first = Richard P. |year=2010 |publisher=University of Alabama Press |isbn=9780817356576 |access-date=7 February 2013}}</ref>

At this time, British doctrine came to recognize two forms of air support; trench strafing (the modern-day doctrine of CAS), and ground strafing (the modern-day doctrine of [[air interdiction]]) – attacking tactical ground targets away from the land battle. As well as strafing with machine-guns, planes engaged in such operations were commonly modified with bomb racks; the plane would fly in very low to the ground and release the bombs just above the trenches.{{citation needed|date=September 2020}}

[[File:Junkers JI.jpg|thumb|The [[Junkers J.I]], a First World War German [[ground-attack aircraft]]]]
The Germans were also quick to adopt this new form of warfare and were able to deploy aircraft in a similar capacity at Cambrai. While the British used single-seater planes, the Germans preferred the use of heavier two-seaters with an additional machine gunner in the aft [[cockpit]]. The Germans adopted the powerful [[Hannover CL.II]] and built the first purpose-built [[ground attack aircraft]], the [[Junkers J.I]]. During the 1918 [[German spring offensive]], the Germans employed 30 squadrons, or ''[[Schlasta]]'', of ground attack fighters and were able to achieve some initial tactical success.<ref name=House2001/>{{page needed|date=July 2012}} The British later deployed the [[Sopwith Salamander]] as a specialized ground attack aircraft, although it was too late to see much action.

During the [[Sinai and Palestine Campaign]] of 1918, CAS aircraft functioned as an important factor in ultimate victory. After the British achieved [[air superiority]] over the German aircraft sent to aid the [[Ottoman Empire|Ottoman Turks]], squadrons of S.E 5a's and D.H. 4s were sent on wide-ranging attacks against German and Turkish positions near the [[Jordan river]]. Combined with a ground assault led by General [[Edmund Allenby]], three Turkish armies soon collapsed into a full rout. In the words of the attacking squadron's official report:

{{quote|No 1 Squadron made six heavy raids during the day, dropped three tons of bombs and fired nearly 24,000 machine gun rounds.<ref name="Airpower" />}}

===Inter-war period===
{{further|Army cooperation aircraft}}
[[Image:Z Force DH9 in air ambulance role.jpg|thumb|left|The British used air power extensively during the interwar period to police areas in the [[Middle East]].]]
The close air support doctrine was further developed in the [[interwar period]]. Most theorists advocated the adaptation of [[fighter aircraft|fighter]]s or [[light bomber]]s into the role. During this period, [[airpower]] advocates crystallized their views on the role of air-power 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.{{Citation needed|date=January 2017}}

The inter-war period saw the use of CAS in a number of conflicts, including the [[Polish–Soviet War]], the [[Spanish Civil War]], the [[Iraqi revolt of 1920]] and the [[Gran Chaco War]].<ref name="Airpower" />

The British used air power to great effect in various colonial hotspots in the [[Middle East]] and [[North Africa]] during the immediate postwar period. The newly formed [[Royal Air force]] (RAF) contributed to the defeat of the Afghan military during the [[Third Anglo-Afghan War#Importance of British airpower|Third Anglo-Afghan War]] by harassing Afghani troops and breaking up their formations. Z Force, an RAF air squadron, was also used to support ground operations during the [[Somaliland campaign (1920)#Actions|Somaliland campaign]], in which the Darawiish king [[Las_Anod#Diiriye_Guure| Diiriye Guure]]'s insurgency<ref name="scr">{{cite book |last1=Omar |first1=Mohamed |title=The Scramble in the Horn of Africa |date=2001 |page=402 |quote=This letter is sent by all the Dervishes, the Amir, and all the Dolbahanta to the Ruler of Berbera ... We are a Government, we have a Sultan, an Amir, and Chiefs, and subjects ... (reply) In his last letter the Mullah pretends to speak in the name of the Dervishes, their Amir (himself), and the Dolbahanta tribes. This letter shows his object is to establish himself as the Ruler of the Dolbahanta}}</ref> was defeated. Following from these successes, the decision was made to create a unified [[RAF Iraq Command]] to use air power as a more cost-effective way of controlling large areas than the use of conventional land forces.<ref>Boyle, Andrew. ''Trenchard Man of Vision'' p. 371.</ref> It was effectively used to suppress the [[Great Iraqi Revolution of 1920]] and various other tribal revolts.

During the Spanish Civil War German volunteer aviators of the [[Condor Legion]] on the Nationalist side, despite little official support from their government, developed close air support tactics that proved highly influential for subsequent [[Luftwaffe]] doctrine.{{citation needed|date=September 2020}}

[[United States Marine Corps Aviation|U.S. Marine Corps Aviation]] was used as an intervention force in support of [[United States Marine Corps|U.S. Marine Corps]] ground forces during the [[Banana Wars]], in places such as [[Haiti]], the [[Dominican Republic]] and [[Nicaragua]]. Marine Aviators experimented with air-ground tactics and in Haiti and Nicaragua they adopted the tactic of [[dive bombing]].<ref name=CorumJohnson_pp23-40>[[#CorumJohnson|Corum & Johnson]], ''Small Wars'', pp. 23-40.</ref>

The observers and participants of these wars would base their CAS strategies on their experience of the conflict. Aviators, who wanted institutional independence from the Army, pushed for a view of air-power 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.{{citation needed|date=September 2020}}

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.{{citation needed|date=September 2020}} 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 would not render ground untrafficable, slowing attacking friendly forces.<ref name=House2001/>{{page needed|date=July 2012}}

Although the prevailing view in official circles was largely indifferent to CAS during the interwar period, its importance was expounded upon by military theorists, such as [[J. F. C. Fuller]] and [[Basil Liddell Hart]]. Hart, who was an advocate of what later came to be known as '[[Blitzkrieg]]' tactics, thought that the speed of armoured tanks would render conventional artillery incapable of providing support fire. Instead he argued that low-flying aircraft could serve as “more mobile artillery” in its place.<ref>{{cite book |url=https://books.google.com/books?id=uq1nV4XObpAC |title=Liddell Hart and the Weight of History |last=Mearsheimer |first= John J. |year=2010 |publisher=Cornell University Press |isbn=978-0801476310 |access-date=7 February 2013}}</ref>

===World War II===
====''Luftwaffe''====
[[File:Bundesarchiv Bild 101I-646-5188-17, Flugzeuge Junkers Ju 87.jpg|thumb|A flight of Ju 87 D-5s over the [[Eastern Front (World War II)|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, it was unique in its willingness to commit forces to CAS. Unlike the Allies, the Germans were not able to develop powerful [[strategic bombing]] capabilities, which implied industrial developments they were forbidden to take according to the [[Treaty of Versailles]].<ref name="ifri">{{cite journal |url=https://www.ifri.org/sites/default/files/atoms/files/fs35bistenenbaum.pdf |title=The Battle over Fire Support: The CAS Challenge and the Future of Artillery |journal=Focus stratégique |volume=35 bis |date=October 2012 |last=Tenenbaum |first=Elie |publisher=Institut français des relations internationales |isbn=978-2-36567-083-8}}</ref> In joint exercises with [[Sweden]] in 1934, the Germans were first exposed to [[dive bomber|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 [[SBC Helldiver|Curtiss Helldiver]], resulting in the [[Henschel Hs 123]], which was later replaced by the famous [[Junkers Ju 87]] ''Stuka''. Experience in the [[Spanish Civil War]] lead to the creation of five ground-attack groups in 1938,{{dubious|date=October 2011|German "ground-attack squadron" is normally understood as Schlachtgeschwader (mainly Henschel Hs 123 and Hs 129), while this text seems to describe Sturzkampfgeschwader ("dive-bombing squadron", mainly Ju 87).}} 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.{{citation needed|date=September 2020}}

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 (Nazi Germany)|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 (although as often as not, the Stukas were used as [[tactical bomber]]s instead of close air support, leaving much of the actual work to the older Hs 123 units for the first years of the war). 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 (World War II)|Eastern front]], the Germans would devise visual ground signals to mark friendly units and to indicate direction and distance to enemy emplacements.{{citation needed|date=September 2020}}

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.{{citation needed|date=July 2012}} 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."<ref name=House2001/>{{page needed|date=July 2012}}

German CAS was also extensively used on the [[Eastern Front (World War II)|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. Luftwaffe's loss of air superiority, combined with a declining supply of aircraft and fuel, crippled their ability to provide effective CAS on the western front after 1943.{{citation needed|date=July 2012}}

====RAF and USAAF====
[[File:Douglas SBD Dauntless dropping a bomb, circa in 1942.jpg|thumb|right|[[United States Navy|U.S. Navy]] [[Douglas SBD Dauntless|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 liaison officer (known colloquially as "tentacles") to accompany Army divisions and brigades. Their report spurred the RAF to create an [[RAF Army Cooperation Command]] and to develop tentacle equipment and procedures placing an Air Liaison Officer with each brigade.<ref>Delve 1994, p. 100.</ref>

Although the RAF was working on its CAS doctrine in London, officers in North Africa improvised their own coordination techniques. In October 1941, [[Arthur Tedder, 1st Baron Tedder|Sir Arthur Tedder]] and [[Arthur Coningham (RAF officer)|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.<ref name=House2001 />{{page needed|date=July 2012}} It was also in the North Africa desert that the [[cab rank (disambiguation)|cab rank]] strategy was developed.<ref>{{cite book |title=Strike from Above: The History of Battlefield Air Attack 1911–1945|pages=181–182 }}</ref> 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|date=May 2009}} The CAS tactics developed and refined by the British during the [[North Africa Campaign|campaign in North Africa]] served as the basis for the Allied system used to subsequently gain victory in the air over Germany in 1944 and devastate its cities and industries.<ref name="Hallion" />

The use of [[forward air control]] to guide close air support (CAS)<ref>{{cite web|url=http://www.mod.uk/NR/rdonlyres/4463968B-8061-4E75-BDC3-05074EFA8AFF/0/20071218_ijwp3_30_U_DCDCIMAPPS.pdf |title=Joint Air Operations Interim Joint warfare Publication 3–30 |pages=4–5 |publisher=MoD |quote=CAS in defined as air action against targets that are in proximity to friendly forces and require detailed integration of each air mission with the fire and movement of these forces |url-status=dead |archive-url=https://web.archive.org/web/20110608001520/http://www.mod.uk/NR/rdonlyres/4463968B-8061-4E75-BDC3-05074EFA8AFF/0/20071218_ijwp3_30_U_DCDCIMAPPS.pdf |archive-date=2011-06-08 }}</ref> aircraft, so as to ensure that their attack hits the intended target and not friendly troops, was first used by the British [[Desert Air Force]] in North Africa, but not by the USAAF until operations in Salerno.<ref>{{cite web|url=https://apps.dtic.mil/sti/pdfs/ADA466970.pdf|archive-url=https://web.archive.org/web/20110604194605/http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA466970&Location=U2&doc=GetTRDoc.pdf|url-status=live|archive-date=June 4, 2011|title=The Twelfth US Air Force Tactical and Operational Innovations in the Mediterranean Theater of Operations, 1943–1944.|author=Matthew G. St. Clair |quote=The use of forward air controllers (FAC) was another innovative technique employed during Operation Avalanche. FACs were first employed in the Mediterranean by the British Desert Air Force in North Africa but not by the AAF until operations in Salerno. This type of C2 was referred to as 'Rover Joe' by the United States and 'Rover David' or 'Rover Paddy' by the British.|publisher=Air University Press Maxwell Air Force Base, Alabama |date=February 2007}}</ref> During the [[North African Campaign]] in 1941 the [[British Army]] and the [[Royal Air Force]] established Forward Air Support Links (FASL), a mobile air support system using ground vehicles. Light reconnaissance aircraft would observe enemy activity and report it by radio to the FASL which was attached at brigade level. The FASL was in communication (a two-way radio link known as a "tentacle") with the Air Support Control (ASC) Headquarters attached to the corps or armoured division which could summon support through a Rear Air Support Link with the airfields.<ref>Ian Gooderson, ''Air power at the Battlefront: Allied Close Air Support in Europe, 1943–45'', p. 26</ref><ref>{{cite news|url=http://findarticles.com/p/articles/mi_hb3101/is_4_53/ai_n29316931/|title=Forward air control: a Royal Australian Air Force innovation |work=Air Power History |first=Carl A. |last=Post |year=2006}}</ref> They also introduced the system of ground direction of air strikes by what was originally termed a "Mobile Fighter Controller" traveling with the forward troops. The controller rode in the "leading tank or armoured car" and directed a "cab rank" of aircraft above the battlefield.<ref>{{cite web |work=Short History of the Royal Air Force |url=http://www.raf.mod.uk/rafcms/mediafiles/F21D57C4_9913_5321_BB9830F0BB762B4E.pdf |publisher=RAF |title=RAF & Army Co-operation |page=147 |url-status=dead |archive-url=https://web.archive.org/web/20110806021956/http://www.raf.mod.uk/rafcms/mediafiles/F21D57C4_9913_5321_BB9830F0BB762B4E.pdf |archive-date=2011-08-06 }}</ref> This system of close co-operation first used by the Desert Air Force, was steadily refined and perfected, during the campaigns in Italy, Normandy and Germany.

[[File:Mobile Fighter Controllers.jpg|thumb|right|British Mobile Fighter Controllers providing [[forward air control]] during World War II]]

By the time the [[Italian Campaign (World War II)|Italian Campaign]] had reached [[Rome]], the Allies had established [[air superiority]]. They were then able to pre-schedule strikes by [[fighter-bomber]] squadrons; however, by the time the aircraft arrived in the strike area, oftentimes the targets, which were usually trucks, had fled.<ref name="Strikefrom">{{Cite book|last=Hallion, Richard. P|url=https://www.worldcat.org/oclc/19590167|title=Strike from the sky: the history of battlefield air attack, 1911–1945|date=1989|publisher=Smithsonian Institution Press|isbn=0-87474-452-0|location=Washington|pages=181–182|oclc=19590167}}</ref> The initial solution to fleeing targets was the British "Rover" system. These were pairings of air controllers and army liaison officers at the front but able to switch communications seamlessly from one brigade to another – hence Rover. Incoming strike aircraft arrived with pre-briefed targets, which they would strike 20 minutes after arriving on station only if the Rovers had not directed them to another more pressing target. Rovers might call on artillery to mark targets with smoke shells, or they might direct the fighters to map grid coordinates, or they might resort to a description of prominent terrain features as guidance. However, one drawback for the Rovers was the constant rotation of pilots, who were there for fortnightly stints, leading to a lack of institutional memory. US commanders, impressed by the British tactics at the Salerno landings, adapted their own doctrine to include many features of the British system.<ref>{{cite web|url=http://www.fac-assoc.org/Ancestry/ancestryofforwardaircontrollersthroughtwwii.htm |title=The Ancestry of Forward Air Controllers |quote=fundamental feature of the system was use of waves of strike aircraft, with pre-briefed assigned targets but required to orbit near the line of battle for 20 minutes, subject to Rover preemption and use against fleeting targets of higher priority or urgency. If the Rovers did not direct the fighter-bombers, the latter attacked their pre-briefed targets. US commanders, impressed by British at the [[Salerno landings]], adapted their own doctrine to include many features of the British system, leading to differentiation of British 'Rover David', US 'Rover Joe' and British 'Rover Frank' controls, the last applying air strikes against fleeting German artillery targets. |author=Charles Pocock |publisher=Forward Air Controllers Association |url-status=dead |archive-url=https://web.archive.org/web/20130825064743/http://www.fac-assoc.org/Ancestry/ancestryofforwardaircontrollersthroughtwwii.htm |archive-date=August 25, 2013 }}</ref>

At the start of the War, the [[United States Army Air Forces]] (USAAF) had, as its principal mission, the doctrine of strategic bombing. This incorporated the unerring belief that unescorted bombers could win the war without the advent of ground troops. This doctrine proved to be fundamentally flawed. However, during the entire course of the war the USAAF top brass clung to this doctrine, and hence operated independently of the rest of the Army. Thus it was initially unprepared to provide CAS, and in fact, had to be dragged "kicking and screaming" into the CAS function with the ground troops. 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.{{citation needed|date=September 2020}}

The situation improved during the [[Italian Campaign (World War II)|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.{{citation needed|date=September 2020}} 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.<ref>{{cite web |url=https://airandspace.si.edu/stories/editorial/stripes-d-day |title=The Stripes of D-Day |first=Allan  |last=Janus |website=[[National Air and Space Museum]] |date=6 June 2014 |access-date=20 November 2016}}</ref><ref>{{cite web |url=http://paul.rutgers.edu/~mcgrew/wwii/usaf/html/DDay.html |title=Army Air Forces and the Normandy Invasion, April 1 to July 12, 1944 |first=Frederick J. |last=Shaw |work=U.S. Air Force |via=Rutgers University |access-date=September 12, 2020 |archive-date=August 31, 2019 |archive-url=https://web.archive.org/web/20190831114958/http://paul.rutgers.edu/~mcgrew/wwii/usaf/html/DDay.html |url-status=dead }}</ref>

In 1944, USAAF commander Lt. Gen. [[Henry H. Arnold|Henry ("Hap") Arnold]] acquired 2 groups of [[SBD Dauntless|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 Apache]]. 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.{{citation needed|date=September 2020}}
[[File:013754 09 Strafing at Gona Buna.JPG|left|thumb|A [[United States Navy|U.S. Navy]] aircraft [[strafing]] Japanese positions during the [[New Guinea campaign]] of the [[Pacific War]], 1942]]
The USAAF saw the greatest innovations in 1944 under General [[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.{{citation needed|date=September 2020}}

[[XIX Tactical Air Command|XIX TAC]], under the command of General [[Otto P. Weyland]] used 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 credited by Patton as having been a key factor in the rapid advance and success of his Third Army.<ref>Spires 2002. {{page needed|date=September 2020}}</ref>

The American Navy and Marine Corps used CAS in conjunction with or as a substitute for the lack of available artillery or naval gunfire in the [[Pacific Ocean theater of World War II|Pacific theater]]. Navy and Marine [[F6F Hellcat]]s and [[F4U Corsair]]s used a variety of [[Aircraft ordnance|ordnance]] such as conventional bombs, rockets and napalm to dislodge or attack Japanese troops using cave complexes in the latter part of the Second World War.<ref name="Barber2">Barber 1946, [https://web.archive.org/web/19980703132559/http://www.history.navy.mil/download/nasc.pdf Table 2].</ref><ref>[https://warfarehistorynetwork.com/daily/wwii/whistling-death-the-chance-vought-f4u-corsair/ "Whistling Death: The Chance-Vought F4U Corsair"] {{Webarchive|url=https://web.archive.org/web/20190625034438/https://warfarehistorynetwork.com/daily/wwii/whistling-death-the-chance-vought-f4u-corsair/ |date=2019-06-25 }}. ''Warfare History Network''. 16 December 2018.</ref>

====Red Air Force====
The [[Soviet Union]]'s [[Red Air Force]] quickly recognized the value of ground-support aircraft. As early as the [[Battle of Khalkhin Gol|Battles of Khalkhyn Gol]] in 1939, Soviet aircraft had the task of disrupting enemy ground operations.<ref>Coox 1985, p. 663.</ref> This use increased markedly after the June 1941 [[Operation Barbarossa|Axis invasion of the Soviet Union]].<ref>Austerslått, Tor Willy. [http://break-left.org/air/il-2.html "Ilyushin Il-2"]. {{Webarchive|url=https://web.archive.org/web/20110515195955/http://break-left.org/air/il-2.html |date=15 May 2011 }} ''break-left.org'', 2003. Retrieved: 27 March 2010.</ref> Purpose-built aircraft such as the [[Ilyushin Il-2]] ''Sturmovik'' proved highly effective in blunting the activity of the ''[[Panzer]]s''. [[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".<ref name="stalinquote"/>

===Korean War===
[[File:Koreacloseairsupport1950.JPEG|thumb|[[Vought F4U Corsair| F4U-5 Corsairs]] providing CAS for U.S. Marines during the [[Korean War]]]]
From Navy experiments with the [[V-1 (flying bomb)#Post-war|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.<ref name=Krulak_pp113-119>[[#Krulak|Krulak]], ''First to Fight'', pp. 113–119.</ref>

Though the Marine Corps continued its tradition of intimate air–ground cooperation in the [[Korean War]], the newly created [[United States Air Force]] (USAF) again moved away from CAS, now to strategic bombers and jet [[interceptor aircraft|interceptor]]s. 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 (United States)|8th Cavalry Regiment]], 1st Cavalry Division (later [[Chief of Staff of the United States Army|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."<ref name=Blair1987_p577>[[#Blair|Blair]] (1987), ''Forgotten War'', p. 577.</ref>

It is unsurprising, then, that [[Douglas MacArthur|MacArthur]] excluded USAF aircraft from the airspace over the [[Battle of Inchon|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 W. Clark|Mark Clark]], to permanently attach an attack squadron to each of the four army corps in Korea. Though the request was denied, Clark allocated many 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 controller]]s (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.{{citation needed|date=September 2020}}

The [[U.S. Army]] wanted a dedicated USAF presence on the battlefield to reduce [[fratricide]], or the harm of friendly forces. This preference led to the creation of the air liaison officer (ALO) position. The ALO is an aeronautically rated officer that has spent a tour away from the cockpit, serving as the primary adviser to the ground commander on the capabilities and limitations of [[airpower]].{{citation needed|date=September 2020}} The Korean War revealed important flaws in the application of CAS. Firstly, the USAF preferred interdiction over [[fire support]] while the Army regarded support missions as the main concern for air forces. Then, the Army advocated a degree of decentralization for good reactivity, in contrast with the USAF-favored centralization of CAS. The third point dealt with the lack of training and joint culture, which are necessary for an adequate air-ground integration. Finally, USAF aircraft were not designed for CAS: "the advent of [[Fighter aircraft|jet fighters]], too fast to adjust their targets, and [[strategic bomber]]s, too big to be used on theatre, rendered CAS much harder to implement".<ref name="ifri"/>

===Vietnam and the CAS role debate===
[[File:F-4C Phantom II of 557th TFS over Vietnam in 1969.jpg|thumb|A USAF [[McDonnell Douglas F-4 Phantom II|F-4 Phantom II]] providing close air support for American armored vehicles during the [[Vietnam War]]]]
During the late 1950s and early 1960s, the US Army began to identify a dedicated CAS need for itself. The Howze Board, which studied the question, published a landmark report describing the need for a helicopter-based CAS requirement.<ref>{{cite web|url=https://www.nytimes.com/1998/12/18/nyregion/gen-hh-howze-89-dies-proposed-copters-as-cavalry.html |title=General HH Howze (Obit) |work=[[The New York Times]] |date=18 December 1998 |access-date=16 April 2012}}</ref> However, the Army did not follow the Howze Board recommendation initially. Nevertheless, it did eventually adopt the use of helicopter [[gunship]]s and [[attack helicopter]]s in the CAS role.<ref>{{cite web |url = https://apps.dtic.mil/sti/pdfs/ADA381779.pdf |archive-url = https://web.archive.org/web/20121007125555/http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA381779 |url-status = live |archive-date = October 7, 2012 |title = Transforming the Force: The 11th Air Assault Division (Test) from 1963–1965 |publisher = dtic.mil |page = 29}}</ref>

Though the Army gained more control over its own CAS due to the development of the helicopter gunship and attack helicopter, the Air Force continued to provide fixed-wing CAS for Army units. Over the course of the war, the adaptation of The Tactical Air Control System proved crucial to the improvement of Air Force CAS.<ref name=":0">{{Cite book |title=Help From Above: Air Force Close Air Support of the Army, 1946-1973 |last=Schlight |first=John |publisher=Air Force History and Museums Publication Program |year=2003 |isbn=0-16-051552-1 |location=Washington, D.C. |pages=300}}</ref> Jets replaced propeller-driven aircraft with minimal issues. The assumption of responsibility for the air request net by the Air Force improved communication equipment and procedures, which had long been a problem. Additionally, a major step in satisfying the Army's demands for more control over their CAS was the successful implementation of close air support control agencies at the corps level under Air Force control.<ref name=":0" /> Other notable adaptations were the usage of airborne Forward Air Controllers (FACs), a role previously dominated by FACs on the ground, and the [[Operation Arc Light|use of B-52s for CAS]].<ref name=":0" />

U.S. Marine Corps Aviation was much more prepared for the application of CAS in the Vietnam War, due to CAS being its central mission.<ref>{{Cite book |title=Close Air Support and the Battle for Khe Sanh |last=Callahan |first=Lieutenant Colonel Shawn |publisher=History Division, United States Marine Corps |year=2009 |location=Quantico, VA |pages=25–27}}</ref> In fact, as late as 1998, Marines were still claiming in their training manuals that "Close air support (CAS) is a Marine Corps innovation."<ref name="mcwp">{{cite news |last1=RHODES |first1=J. E. |title=CLOSE AIR SUPPORT |url=https://www.trngcmd.marines.mil/Portals/207/Docs/TBS/MCWP%203-23.1%20Close%20Air%20Support.pdf |work=MCWP 3-23.1 |agency=U.S. Marine Corps |publisher=DEPARTMENT OF THE NAVY |date=30 July 1998}}</ref> One of the main debates taking place within the Marine Corps during the war was whether to adopt the helicopter gunship as a part of CAS doctrine and what its adoption would mean for fixed-wing CAS in the Marine Corps.<ref>{{Cite journal |last=Krueger |first=Colonel S.P. |date=May 1966 |title=Attack or Defend |journal=Marine Corps Gazette |volume=50 |pages=47 }}</ref> The issue would eventually be put to rest, however, as the helicopter gunship proved crucial in the combat environment of Vietnam.
[[File:Calling in fire support 140424-A-QU939-197.jpg|thumb|[[United States Army|U.S. Army]] soldiers coordinating close air support. In the background is the aforementioned close air support, an [[Boeing AH-64 Apache|AH-64E Apache Guardian]] [[attack helicopter]].]]
Though helicopters were initially armed merely as defensive measures to support the landing and extraction of troops, their value in this role led 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 use 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 missile]]s, 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 back 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 was reiterated between ground commanders and aviators. Nevertheless, the US Army incrementally gained increased control over its CAS role.<ref name="Rivalry">{{cite web |url=http://carl.army.mil/download/csipubs/horwood.pdf |title=Interservice Rivalry and Airpower in the Vietnam War – Chapter 5 |publisher=Carl.army.mil |access-date=16 April 2012 |archive-url=https://web.archive.org/web/20111009064121/http://carl.army.mil/download/csipubs/horwood.pdf |archive-date=9 October 2011 |url-status=dead }}</ref>

In the mid-1970s, after Vietnam, the USAF decided to train an [[Enlisted rank|enlisted]] force to handle many of the tasks the ALO was saturated with, to include [[terminal attack control]]. Presently, 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]].{{citation needed|date=September 2020}}

===NATO and AirLand Battle===
Since their 1977 introduction into modern military practice for close air support purposes, General [[Crosbie E. Saint]] provided the [[AH-64 Apache]] the doctrinal cover for use in [[AirLand Battle]] operations such as in the [[NATO]] European theatre.