The present essay, studying the historical, social, political, and military factors, traces the development of ideas culminating in the detention. Considering the affair in this manner should more clearly explain the "why" of Japanese removal. Particularly, the concept of "military necessity," the Army's major reason for evacuation, is considered with emphasis on factors which contributed to the development of this position. The role of Lieutenant General John L. DeWitt, the primary advocate of removal based on necessity, is explored.