This thesis is a biographical portrait of Eugene H. Dooman, a Japan specialist in the American Foreign Service, 1912 - 1945. As such, it raises a series of related questions. What was an expert? How did American Foreign Service Officers develop their expertise? Finally, what effect did career officers have on Japanese-American relations during the years between passage of the Immigration Act of 1924 and the end of World War II in the Pacific? Based on research in the diplomatic papers of the United States Department of State and Dooman's private papers~ the essay traces his career from its earliest stages when he entered the student interpreter corps and his subsequent consular service to his rise as Counselor of Embassy in Tokyo and his final years in the Office of Far Eastern Affairs. Close attention is given to Dooman's efforts to prevent the outbreak of war between Japan and the United States, 1937-1941, and his attempts to influence postwar planning for Japan and American peace offers in 1945. Despite his Japanese language proficiency, his knowledge and experience, Dooman's advice often went unheeded, a reflection of American ambivalence towards the need for expertise in dealing with the peoples and cultures of East Asia.