The US embargoed Japan's oil, which led to the attack on Pearl Harbor in 1941.

Judge against the historical record as of 2018-11-11. True: the US imposed an oil embargo on Japan (summer 1941, alongside the asset freeze), Japan attacked Pearl Harbor on 7 December 1941, and mainstream historians treat the oil embargo as a principal cause of Japan's decision to go to war. Mostly true: both events and the year are confirmed and the embargo is widely seen as a major contributing cause, but the claim simplifies a causal chain that also included the asset freeze, the Hull note and the China war. Mixed: the embargo happened but historians treat it as only one of many roughly equal causes. Mostly false: the embargo is generally seen as a minor factor in the attack. False: there was no US oil embargo before the attack, or the attack was not in 1941.

Set before the research began.

1. E1 Pearl Harbor 1941: The First Energy War Center for International Maritime Security (CIMSEC), reprinting The Foreign Service Journal · 30 January 2019

   “On July 26th President Roosevelt ordered the freezing of all Japanese funds and other assets in the United States and the placing of all petroleum exports to Japan under embargo subject to license.”

2. E2 Pearl Harbor 1941: The First Energy War Center for International Maritime Security (CIMSEC), reprinting The Foreign Service Journal · 30 January 2019

   “The Japanese air raid on Pearl Harbor of December 7, 1941”

3. E3 Pearl Harbor 1941: The First Energy War Center for International Maritime Security (CIMSEC), reprinting The Foreign Service Journal · 30 January 2019

   “Oil was not the primary cause of the steady deterioration of relations between the United States and Japan, but once employed as a weapon it made hostilities inevitable.”

4. E4 Prelude to the attack on Pearl Harbor - Wikipedia Wikipedia · 7 October 2007

   “That move prompted the U.S. to embargo all oil exports, which led the Imperial Japanese Navy (IJN) to estimate it had less than two years of bunker oil remaining and to support the existing plans to seize oil resources in the Dutch East Indies.”

E1 records that President Roosevelt froze Japanese assets and placed all petroleum exports to Japan under embargo. E2 dates the Pearl Harbor attack to December 7, 1941. E4 says the embargo led the Japanese navy to support plans to seize oil in the Dutch East Indies. E3 calls oil not the primary cause of the worsening relations but says it made hostilities inevitable. That makes the embargo a major contributing cause within a longer causal chain that also included the asset freeze and earlier tensions, which fits the "mostly true" criterion.