Rostow spent a year at Cambridge University as the Pitt Professor of American History and Institutions. He was professor of economic history at the Massachusetts Institute of Technology (MIT) from 1950 to 1961, and a staff member at the Center for International Studies (CIS) at the MIT from 1951 to 1961. The outbreak of the Korean War decisively altered Rostow's thinking about the Soviet Union. Until the Korean War, Rostow had believed that the Soviet system would ultimately "mellow" on its own accord and he had also viewed the Cold War as a largely diplomatic conflict as opposed to a military struggle. The North Korean aggression against South Korea convinced him that the Cold War required a more militarized foreign policy as he called for greater defense spending in a speech in the fall of 1950 so a "larger full mobilization could be carried out quickly." To pay for the higher amount of defense spending, Rostow urged the American people to accept the need for a "very high level of taxation appropriated equally".