In November 1941, following several line and staff appointments, Commander Prince Takamatsu became a member of the Operation Planning Section of the Navy General Staff. In November 1942, he was promoted to captain, and in August 1944, he was appointed deputy head of the Yokosuka Gunnery School.
As a liberal thinker in the navy and within the Imperial family, Prince Takamatsu was highly critical of the government's decision to go to war with the United States, and during the war, he advocated an early peace with the Allies. Elements in Japan opposed to Premier General Tojo Hideki, including Prince Konoe Fumimaro, saw in Prince Takamatsu a possible candidate for prime minister. Takamatsu died in Tokyo on 3 February 1987. His posthumously published diaries are an important source for the study of Japanese political history of the 1930s and 1940s. Tohmatsu Haruo
Bix, Herbert P. Hirohito and the Making of Modern Japan. New York: Harper Collins, 2000.; Large, Stephen J. Emperor Hirohito and Showa Japan: A Political Biography. London and New York: Routledge, 1992.; Takamatsu Nobuhito. Takamatsunomiya nikki (Diaries of Prince Takamatsu). 8 vols. Tokyo: Chuokoronsha, 1995–1997.; Wetzler, Peter. Hirohito and War: Imperial Tradition and Military Decision Making in Prewar Japan. Honolulu: University of Hawaii Press, 1998.