Short answers, pulled from the story.
The Empire of Japan launched a surprise military strike on the United States Pacific Fleet at its naval base at Pearl Harbor on the 7th of December 1941. This attack occurred while the U.S. remained a neutral country in World War II.
Admiral Isoroku Yamamoto planned the attack as a pre-emptive strike on the Pacific Fleet based at Pearl Harbor since 1940. Full-scale planning began early in 1941 under Rear Admiral Ryūnosuke Kusaka with assistance from Commander Minoru Genda.
Ninety minutes after it began, the attack ended leaving 2,403 Americans killed and 1,178 wounded. Eighteen ships were sunk or run aground including five battleships.
President Franklin D. Roosevelt delivered his famous Day of Infamy speech to Congress less than an hour after requesting formal declaration of war on December 8. Congress obliged his request immediately.
Admiral Isoroku Yamamoto planned the attack as a pre-emptive strike on the Pacific Fleet based at Pearl Harbor since 1940 to prevent American interference with Japan's planned actions in Southeast Asia. Leaders subscribed to Alfred Thayer Mahan's decisive battle doctrine focusing on maximum battleship destruction.