This article argues that the United States government intensified its research on nuclear fission and decided to build the atomic bomb due to the manipulative efforts of Vannevar Bush. The author contends that In the face of enormous scientific uncertainty and a lack of consensus within the scientific community, Bush manipulated the bureaucracy and opinions within the government to conclude that it was necessary to embark on a full-scale commitment to the construction of an atomic bomb. A detailed account of the chain of events that led to the decision to construct the atomic bomb is provided. Bush’s political motivations are also discussed. The author believes that Bush's efforts were largely successful because he had the ear of President Roosevelt. The article provides a detailed example of a behind-the-scenes decision-making process in U.S. government-sponsored research in the important fields of nuclear fission and atomic bomb building.