Yonai retired from naval service before becoming prime minister because he considered the premiership a civilian office. Emperor Hirohito selected him amid a shortage of trusted alternatives. Yonai opposed the Tripartite Pact and favored pro-British and pro-American policies. When the Army Minister resigned, the constitutional requirement for serving military ministers made the cabinet unsustainable. Yonai resigned on 21 July 1940, and Japan signed the pact with Germany and Italy on 27 September.
Chapter · 8:20-10:11
A premiership opposed to the Tripartite Pact
Yonai's 1940 government resisted alignment with Germany and Italy, until Japan's constitutional military-minister rules helped force his resignation.