After graduating from the Army Academy (1905) and the Army War College (1916), Yamashita was an officer for the Army General Staff Office. He rose rapidly through the ranks of the Imperial Army, eventually becoming the highest-ranking general of its air force.

An able strategist, he trained Japanese soldiers in the technique of jungle warfare and helped conceive the military plan for the Japanese invasion of the Thai and Malay peninsulas in 1941–42. In the course of a 10-week campaign, Yamashita's 25th Army overran all of Malaya and obtained the surrender of the huge British naval base at Singapore on Feb. 15, 1942. Soon afterward Yamashita was retired by Prime Minister Tojo Hideki to an army training command in Manchuria, and he did not see active service again until after Tojo's fall in 1944, when he was sent to command the defense of the Philippines. His forces were badly defeated in both the Leyte and the Luzon campaigns, but he held out until after the general surrender was announced from Tokyo in August 1945. Yamashita was tried for war crimes, and, though he denied knowing of atrocities committed under his command, he was convicted and eventually hanged.