The United States declared war on Japan December 8, 1941. President Franklin Roosevelt went before the US Congress and made his historical statement ,”Yesterday, December 7, 1941—a date which will live in infamy—the United States of America was suddenly attacked by naval and air forces of the Empire of Japan.” Twenty one minutes after this speech the US Senate voted 82 for and 0 against to declare war. The US House of Representatives voted minutes later with a vote of 388 for and 1 against.
The declaration of war was not taken lightly since the repercussions were so complex. It was likely Germany and Italy would declare war against the US and Germany was a stronger force than the US. The US was not ready to get into a war that they were not going to win but the Japanese bombed Pearl Harbor the day before and emotions were suddenly united and strong.
On December 7 the US decoded several messages from Japan stating that diplomatic relations with the US must be broken. The US war department determined that the Hawaii was at risk for attack and tried to contact Hawaiian military officials, but radio contact was broken and delays prevented the alert to reach military headquarters in time. The Japanese attack force bombed Pearl Harbor and took Hawaii totally by surprise.
The attack was under the command of Admiral Nagumo, consisting of six carriers with 423 plans. The attack came in two waves. The first attack targeted US airfields and battleships, and the second wave targeted ships and the shipyard. Five battleships were sunk and eight more were damaged. There were 2335 servicemen and 68 civilians that were killed in the attack and 1178 people were wounded.
The nation was shocked. Public sentiment regarding involvement in the war changed to full support. The nation united behind President Roosevelt and many US youth volunteered to defend their country. This was no longer Europe’s war.
And what caused Japan to attack the US?
The US was supplying arms and money to the forces against Germany; so in essence the US had already taken a stance. Plus, the US decided to stop selling oil and scrap metal to Japan. The US knew that there was conflict between the two countries and President Roosevelt had sent messages to the Emperor of Japan appealing for peace. The war department was on alert and decoding messages from Japan. When they intercepted messages indicating Hawaii might be a target the radio systems were not functioning well enough to warn Hawaii in time to ensure their safety.
While each country got involved for their own reasons, France, Poland, and the United Kingdom were the first to join the “Allied Forces”. This anti-German coalition started at the beginning of the war September 1939. Eventually, the British Empire, the Union of Soviet Socialist Republics, and the United States of America became known as "The Big Three". Other Allies included Australia, Belgium, Brazil, Canada, China, Czechoslovakia, Ethiopia, Greece, India, Mexico, the Netherlands, New Zealand, Norway, the Philippine Commonwealth, Poland, the Union of South Africa, and Yugoslavia.