Between the world wars, Brett graduated from the Command and General Staff School in 1930 and the Army War College in 1936. Promoted to brigadier general in 1939, he served as chief of the Matériel Division at Wright Field, Ohio, from 1939 to 1940. In October 1940, promoted to major general, he was named acting chief of the air corps.
Shortly after the United States entered World War II, he took command of U.S. Army forces in Australia, with responsibility for turning Australia into a support base. For a brief time in early 1942, Brett, who was now a lieutenant general, served as deputy commander of the American-British-Dutch-Australian (ABDA) Command, headquartered on Java in the Netherlands East Indies. Following his return to Australia, Brett became commander of the Fifth Air Force and deputy supreme commander and head of all air forces in the Southwest Pacific Area.
From the outset, Brett's relations with General Douglas MacArthur, commander of SWPA, were strained. MacArthur saw him as too close to Australian politicians, believed he had too many Australians in command and administrative positions, and saw him as responsible for the poor performance of SWPA units in combat. In Brett's defense, it must be pointed out that SWPA suffered from a lack of supplies and trained staff officers and from ill-equipped aircraft. But Brett did not have the confidence of MacArthur, and in the summer of 1942, he was replaced by Major General George Kenney.
In November 1942, Brett became head of the Caribbean Defense Command, a post he held until the end of the war. He retired in March 1946 and died in Winter Park, Florida, on 2 December 1963.
John Kennedy Ohl
Craven, Wesley Frank, and James Lea Cate. Army Air Forces in World War II. Vol. 1, Plans and Early Operations: January 1939 to August 1942. Chicago: University of Chicago Press, 1948.; Griffith, Thomas E. MacArthur's Airman: General George C. Kenney and the War in the Southwest Pacific. Lawrence: University Press of Kansas, 1998.; James, D. Clayton. The Years of MacArthur. Vol. 2, 1941–1945. Boston: Houghton Mifflin, 1975.