On the morning of December 7, 1941, Japanese planes bombed Pearl Harbor – a U.S. naval base on the island of Oahu – destroying or damaging 18 ships and over 300 aircraft and killing or wounding almost 3,500 Americans. The next day, President Franklin D. Roosevelt signed a declaration of war against Japan.

A year earlier, when Japan signed the Tripartite Pact with Germany and Italy creating the Axis Powers, its relations with the U.S. had already been deteriorating. Japan had been aggressive in its dealings with other countries and in retaliation, the U.S. was considering further trade restrictions on the materials Japan needed. One year before the Tripartite Pact was signed, Germany invaded Poland causing France and Great Britain to declare war on Germany, the start of WWII. With the attack on Pearl Harbor, the U.S. entered WWII and Italy became the enemy.