In 1975, U.S. Army Center of Military History commissioned a report on the History of Strategic Air and Ballistic Missile Defense, Volume I (1945-1955) and Volume II (1956-1972), which was part of a larger study of the strategic arms competition that developed between the United States and the Soviet Union after World War II. The report addresses each country's approach to civil defense against the threat from the air and each country's emphasis on specific elements of air defense strategy at various periods between 1945 and 1972. Two central questions concerned the U.S. and Soviet defense planners: "How might we be attacked?" and "How shall we defend our country?"