This study in the Historical Analysis Series examines a subject of importance not only to the Army but also to the Air Force: the origin and development of American close air support doctrine and practice in World War II. The idea for the study resulted from a review of the Memorandum of Understanding between the Army and Air Force chiefs of staff, concluded on 22 May 1984, and of the initiatives that emerged from that historic document, particularly Initiative 24, which reaffirmed the Air Force's mission to provide close air support to the Army. The project has been a cooperative effort between the U.S. Army Center of Military History and the U.S.A.F. Office of Air Force History; an Air Force historian was assigned to write the study under the supervision of the Center of Military History. The resulting work, ultimately the best judgment of the author based on historical evidence, is titled A Pattern for Joint Operations: World War II Close Air Support, North Africa. The concentration is on the North African campaign because that was the first major large-unit test of American ground armies in World War II, and in that campaign the basic system of close air support for American ground and air forces in World War II was first worked out. Close air support doctrine both then and now is critical to the services. As this study demonstrates, the doctrine that had been conceived and practiced prior to the first American battles of World War II fell apart in the mud and fog of Tunisia. Both air and ground commanders in 1941 recognized the necessity of close cooperation between the staffs and forces in joint and combined forces. What they had to learn in 1942 was the degree to which close air support doctrine tested that cooperation and required alteration. The struggle of ground and air leaders to define and construct a command and control system, and ultimately to allocate and commit precious air resources to requisite ground missions, has as many lessons today as it did more than forty years ago.