Pearl Harbor Brings the United States Into World War II
A surprise attack on a Sunday morning ends American neutrality
Quick facts
- Attack
- December 7, 1941, Pearl Harbor, Hawaii
- American dead
- Over 2,400 servicemen
- FDR's speech
- December 8, 1941, "a date which will live in infamy"
- Result
- U.S. entry into World War II
What happened
On the morning of Sunday, December 7, 1941, Japanese carrier aircraft launched a surprise attack on the U.S. Pacific Fleet at Pearl Harbor, Hawaii. In less than ninety minutes Japanese planes destroyed or damaged 19 U.S. warships and 300 aircraft and killed over 2,400 American servicemen, nearly half of them aboard the battleship USS Arizona, which sank after a bomb ignited its forward magazine. The next day, December 8, President Roosevelt addressed Congress, calling December 7 a date which will live in infamy and asking it to recognize that a state of war existed with Japan. Congress declared war almost unanimously, with a single dissenting vote. Days later Germany and Italy declared war on the United States, bringing the country fully into World War II.
Why it matters
Pearl Harbor ended the long American debate over whether to enter the war and united the country behind total mobilization. The United States became the decisive industrial and military power of the Allied coalition, and the war it now joined would transform the nation into a global superpower and reshape the postwar world.
How we know
Roosevelt's war message survives in the National Archives, and the attack's casualties and damage are documented in Navy records and the histories maintained by the National WWII Museum.
Sources
- National Archives. Joint Address to Congress Leading to a Declaration of War Against Japan (1941) · Primary source (author-declared)archives.gov · Cited as a "primary" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
- The National WWII Museum. Pearl Harbor, December 7, 1941 · Reputable sourcenationalww2museum.org · The domain "nationalww2museum.org" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
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Related timelines
- World War II → · This is the American entry into World War II; see the World War II timeline for the wider war in Europe and the Pacific from 1939 to 1945.