Who was the Prime Minister of Japan when Japan declared war on the US?

The story behind the answer

Hideki Tojo was Japan’s Prime Minister—and also War Minister—when Japan declared war on the United States on December 8, 1941 (Tokyo time), immediately following the attack on Pearl Harbor. Taking office in October 1941, Tojo led the militarist cabinet that approved war after diplomacy collapsed, and the Imperial Rescript declaring war was issued under Emperor Hirohito.

To avoid confusion: Fumimaro Konoe was Tojo’s predecessor who tried and failed to reach a diplomatic settlement; Hirohito was the Emperor, not the Prime Minister; and Admiral Isoroku Yamamoto masterminded the Pearl Harbor strike. Memory tip: “Tojo took over—two months to total war.”