A graduate of the Imperial Military Academy and the Military Staff College, Tōjō served briefly as military attaché in Japan's embassy in Berlin after World War I. He was an esteemed administrator and skillful field commander and became noted as a stern disciplinarian. In 1928 he was made commander of the lst Infantry Regiment, which in 1936 participated in the mutiny of the Tokyo garrison. In 1937 he was named chief of staff of the Kwantung Army in Manchuria. He returned to Tokyo in 1938 as vice-minister of war and was one of the leading advocates of Japan's Tripartite Pact with Germany and Italy (1940). In July 1940 he was appointed minister of war in the cabinet of Premier Prince Konoe Fumimaro. Tōjō succeeded Konoe as prime minister on October 16, 1941, and pledged his government to a Greater East Asia program, a “New Order in Asia.” He retained control of the ministry of war and was also minister of commerce and industry from 1943.

A hardworking and efficient bureaucrat, Tōjō was also one of the most aggressive militarists in the Japanese leadership. He led his country's war efforts after the attack on the U.S. base at Pearl Harbor, December 7, 1941, and under his direction smashing victories were initially scored throughout Southeast Asia and the Pacific. After prolonged Japanese military reverses in the Pacific, Tōjō assumed virtual dictatorial powers, taking over the post of the chief of the General Staff. But the successful U.S. invasion of the Marianas so weakened his government that he was removed as chief of staff on July 16, 1944, and on July 18 his entire cabinet resigned.

On September 11, 1945, after Japan's formal surrender, Tōjō shot himself in a suicide attempt, but he was nursed back to health and on April 29, 1946, with other Japanese wartime leaders, was indicted and tried for war crimes before the International Military Tribunal for the Far East. He was found guilty and hanged.