Pearl Harbor Draws Japan Into War With the United States
An oil embargo and a decision to expand into Southeast Asia lead Japan to attack the U.S. Pacific Fleet
Quick facts
- Attack date
- 7 December 1941
- Target
- U.S. Pacific Fleet, Pearl Harbor, Hawaii
- Context
- U.S. oil embargo; Japanese expansion into Southeast Asia
- Result
- U.S. declares war on Japan, 8 December 1941
What happened
By late 1941 a U.S. oil embargo, imposed in response to Japan's expansion in China and Indochina, left Japan facing what the Office of the Historian describes as "serious shortages," convinced its leaders they had no path forward but to act. On 7 December 1941 Japanese aircraft bombed the U.S. fleet at Pearl Harbor, aiming to cripple American naval power in the Pacific before Japan moved into Southeast Asia, where the United States held greater strategic interests. "The following day, the United States declared war on Japan, and it soon entered into a military alliance with China," bringing America fully into the Second World War.
Why it matters
Pearl Harbor transformed a regional war in Asia into a global conflict and brought the full industrial and military weight of the United States against Japan, a mismatch in resources that Japan's own naval planners had warned could not be sustained in a prolonged war.
How we know
The attack and the diplomatic sequence leading to it are documented in official U.S. and Japanese government and military records, including the intercepted diplomatic communications analyzed by U.S. codebreakers before and after the attack.
Sources
- Office of the Historian, U.S. Department of State. Opening to Japan / Pearl Harbor · Reputable sourcehistory.state.gov · The domain "history.state.gov" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
- Office of the Historian, U.S. Department of State. Opening to Japan / Pearl Harbor · Reputable sourcehistory.state.gov · The domain "history.state.gov" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
See something wrong? . Corrections with a source get fixed fastest.
Related timelines
- World War II → · See the World War II timeline for the Pacific War's course after Pearl Harbor and the wider global conflict.