Field Manual 100-20: The ‘Declaration of Independence’ for tactical airpower

  • Published
  • By Dr. Silvano Wueschner
  • Air University

On February 14, 1943, Field Marshal Erwin Rommel, commander of the German Afrika Korps in North Africa, launched a major offensive against Allied positions at the Kasserine Pass in Tunisia, North Africa.

Within days, the rapid advance of the Afrika Korps, supported by German aircraft, nearly overran the entire Allied position, including several forward airfields, in Tunisia. This battle became the first major defeat of U.S. forces in Africa.

During the battle, few U.S. aircraft provided close air support for U.S. ground troops because the air support commander could not provide meaningful operational input, the result of current tactical airpower doctrine embodied in War Department Field Manual 31-35, Aviation in Support of Ground Forces.

However, out of this defeat came the independence of U.S. tactical airpower from Army ground commanders with the publication of FM 100-20, The Command and Employment of Air Power, on July 21, 1943.

The field manual is sometimes called the “Declaration of Independence” for tactical airpower.

The battle at Kasserine Pass was a prime example of how dogma had subsumed doctrine; in this case, the stubborn adherence to FM 31-35. This regulation stipulated that the air support commander normally functioned under the Army theater, or task force, commander. He assigned ground attack missions as the needs of the ground forces developed for that ground force commander. Because the perceived needs of ground forces restrained the air support commander, he could not allocate attack missions to attend to Air Corps’ needs until after the battle took place. This doctrine limited his authority to allocate tactical airpower to other, potentially more-threatened, areas of the theater. This out-of-date doctrine produced a breakdown in communication, inefficient use of available theater-wide air assets and equally important, a breakdown in trust between the air support commander and Army field commanders.

The disaffection between the adherents of tactical airpower and those of strategic airpower had surfaced in the 1920s when strategic airpower advocates sought to achieve autonomy from ground force commanders who insisted that the Air Corps’ mission remain inextricably bound to ground operations. This debate ultimately led to the activation of the General Headquarters Air Force in 1935 and the centralization of all combat air units in the continental United States under it.

While it represented a compromise between the two factions, the lines of authority were not clear. In the continental United States, General Headquarters Air Force exercised control over its combat units, but ground commanders had control over airfields and the administration of personnel. Overseas (and potential future combat theaters), ground commanders retained operational control of air units as well. The Headquarters Air Corps developed airpower doctrine, oversaw the training of personnel and acquired aircraft.

In practice, this division of authority did not yield the kind of unified command required to achieve a direct line of authority and with it, timely input on air matters in combat. In 1941, for example, Army Chief of Staff Gen. George C. Marshall and Secretary of War Henry Stimson were concerned about the lack of timely responses on air matters from the War Department General Staff. Stimson proposed “to place our air arm under one responsible head.”  In late March 1941, Marshall directed Lt. Gen. Henry “Hap” Arnold, deputy chief of staff for Air and chief of the Air Corps, to coordinate on all air matters.

On June 20, 1941, Army Regulation 95-5 created the Army Air Forces. While this step was a welcome step in the direction of an independent air force, the fact remained, as Spaatz noted, that “airmen still disliked both the degree of control” exercised by Army General Headquarters over the Army Air Force units as well as the influence that the Army War Plans Division had on air planning. Arnold argued for the establishment of an “air staff, unification of the air arm under one commander and equality with the ground and supply forces.” The humiliating events at Kasserine Pass would underscore the validity of Arnold’s position.

The debacle at Kasserine took place in the midst of major Allied command and control changes, designed primarily to remedy the breakdown in trust over air-ground cooperation in the North African campaign. In late December 1942, U.S. military leaders had begun discussions about adopting the “centralized control, decentralized execution” model that Royal Air Force Air Marshal Arthur Coningham had developed for the RAF Western Desert Air Force in Egypt. Coningham firmly believed that a “centralized air command with co-equal status between air and ground commanders was a significant change in emphasis, employment and coordination of tactical air power with the army.”  This system proved instrumental in stopping the Axis offensive at El Alamein, Egypt, in July 1942.

The Kasserine debacle served as the catalyst for American efforts to improve air-ground communications and also hastened the demise of FM 31-35. Moreover, it gave a revived impetus for an independent air force which would no longer be wedded to an impossible command structure whereby ground commanders exercised control over operational air units.

During spring 1943, Army Air Force leaders incorporated Coningham’s concepts of “centralized control, decentralized execution” into FM 100-20. Furthermore, FM 100-20 gave command of AAF tactical air units directly to AAF operational commanders. AAF leaders, such as Arnold, enthusiastically endorsed FM 100-20 with its unwritten goal for a separate air service. As one writer put it, it was the tool needed “to remove the restraints of army [ground] commanders’ control over aviation and was the real declaration of independence by the U.S. Army Air Force.”