On December 7, 1941, a quiet sunny day turned into a nightmare at the US Naval Base at Pearl Harbor, Hawaii. The first sign of trouble occurred at about 4 AM when the USS Condor, a minesweeper, spotted a periscope and, noting that no submarines were supposed to be in the area, notified a nearby destroyer. At about 7 AM, the USS Ward fired depth charges at the submarine, apparently sinking it.
It was later discovered that the submarine had been one of five midget submarines sent into Pearl Harbor to fire torpedoes at the fleet stationed there. The Pacific Fleet Commander was notified, who sent out another destroyer, but did not sound the alarm.
At 7:55 AM, Japanese dive bombers came in without warning and began bombing the airfields. The base was caught entirely off guard and much of the defenses were destroyed in the initial bombing run.
A few moments later, planes dropped torpedoes into the water, striking the USS Helena, Utah, and Raleigh. Soon after, more planes arrived, torpedoing the USS Nevada, Oklahoma, West Virginia, and California. The torpedoes caused a great deal of damage to all of these ships, tearing open the hulls.
On the final bombing run, the bombers targeted the USS Arizona, which exploded, the USS Pennsylvania, and three destroyers. By this time, the sailors were more organized and inflicted heavy casualties on the bombers using anti-aircraft guns. Luckily, no carriers were in the harbor at the time, but the Japanese had still destroyed most of the United States Navy's Pacific force.
The Japanese had planned the bombing very well and assigned all six of their aircraft carriers to the mission. This gave them a total of 420 planes to use in the attack, all under the command of Vice Admiral Chuichi Nagumo. The force departed in total secrecy from Japan on November 26, 1941, reaching striking distance of Hawaii in about a week and a half.
The attack had come without any warning and completely caught the United States off guard. The horrified country immediately rallied against the Japanese and, the following day, president Franklin Delano Roosevelt gave a speech before congress, asking them to declare war on Japan.