In 1945, immediately after the war, Rostow became assistant chief of the German-Austrian Economic Division in the United States Department of State in Washington, D.C. Rostow was invited to part in the United States Strategic Bombing Survey (USSBS), an assessment of the effects of the strategical bombing campaign on Germany's economy, but he declined. Several of Rostow's future foes in the 1960s such as George Ball, John Kenneth Galbraith and Arthur M. Schlesinger Jr. did take part in the USSBS, and came away convinced that the strategical bombing campaign did not cripple the German economy as its advocates had promised, an experience that led these men to doubt the efficacy of bombing North Vietnam. Through the "Oil Plan" did indeed work as Rostow had promised, those taking part in the USSBS also noted that German industrial production peaked in December 1944, which led them to doubt the effects of strategical bombing as a way of breaking a nation's economy. In 1946, he returned to Oxford as the Harold Vyvyan Harmsworth Professor of American History. In 1947, he became the assistant to the Executive Secretary of the Economic Commission for Europe, and was involved in the development of the Marshall Plan. One of Rostow's colleagues recalled: "In early 1946, Walt Rostow had a revelation that the unity of Germany could not be achieved without the unity of Europe, and that the unity of Europe could best be approached crabwise through technical cooperation in economic matters, rather than bluntly in diplomatic negotiations". Rostow's writings on the subject of European economic unity attracted the attention of Undersecretary of State Dean Acheson, and ultimately Jean Monnet, the French diplomat regarded as the "father" of the European Coal and Steel Community of 1951 that became the European Economic Community in 1957.