As the Cold War intensified, oil negotiations stalled, and the Republican President Dwight D. Eisenhower replaced Democratic President Harry S. Truman, the United States helped destabilize Mosaddeq on the theory that "rising internal tensions and continued economic deterioration...might lead to a breakdown of government authority and open the way for at least a gradual assumption of control" by Iran's well organized Tudeh communist party. In spring and summer 1953, the Central Intelligence Agency and MI6 carried out Operation Ajax, conducted from the American Embassy in Tehran, helping to organize a coup d'état to overthrow the Mossadeq government. The operation initially failed, and the Shah fled to Italy, but a second attempt succeeded, and Mosaddeq was imprisoned.