In 1940 Lovett's continuing interest in aviation and his concern to build up U.S. aerial production capacities led Secretary of War Henry L. Stimson to appoint him assistant secretary of war for air. For almost five years Lovett supervised the immense World War II buildup of American airpower and helped the Army Air Forces to retain some autonomy, a policy that later made it easier for the Army Air Forces to become an independent service arm.
After the war Lovett returned to private life until 1947, when his former superior George C. Marshall, to whom he was particularly close and whom President Harry S. Truman had just appointed secretary of state, persuaded Lovett to become undersecretary of state. He remained in office until late 1948, overseeing the development of the Marshall Plan and the North Atlantic Treaty Organization (NATO). In September 1950, when Marshall became secretary of defense during the Korean War, Lovett once again served as his deputy, supervising a major military buildup and succeeding Marshall when the latter retired in late 1951.
Lovett left office when the Truman administration ended, but successive presidents repeatedly sought his views on assorted foreign policy issues, regarding him as a key member of the Wise Men, the establishment figures who presided over the mid-twentieth-century expansion of American international power. In the mid-1950s Lovett presciently warned that the Central Intelligence Agency (CIA) had become overly enamored of covert operations. During the 1962 Cuban Missile Crisis President John F. Kennedy consulted Lovett, who counseled moderation. He was one of the senior advisors who, by late 1967, was disillusioned with the U.S. involvement in Vietnam, even though he did not attend the meeting of such Wise Men in March 1968 that ultimately counseled President Lyndon B. Johnson to withdraw American forces from Vietnam. Lovett died in Locust Valley, Long Island, New York, on 14 September 1986.
Fanton, Jonathan. "Robert A. Lovett: The War Years." Unpublished PhD diss., Yale University, 1978.; Isaacson, Walter, and Evan Thomas. The Wise Men: Six Friends and the World They Made; Acheson, Bohlen, Harriman, Kennan, Lovett, McCloy. New York: Simon and Schuster, 1986.; Sherry, Michael S. The Rise of American Air Power: The Creation of Armageddon. New Haven, CT: Yale University Press, 1987.