Data commentary
August 1, 1941
The US bans oil exports to all aggressor countries (this includes motor fuel and lubricating oil for airplanes).

“(7) The Command Freezing Japanese Assets on July 25” (1 page)
(Offered by the Diplomatic Museum at the Ministry of Foreign Affairs)
On Friday, August 1 1941, The US announces a ban on oil exports to “aggressor countries,” including Japan. This was just as acting Secretary of State Wells had warned Ambassador to the United States Kichisaburo Nomura on July 24. Thus, Japan begins to face serious problems regarding the procurement of resources.
Document 1: B02030753200 File of Important Materials Relating to Diplomatic Relations with the United States, Vol. 3 – Speeches, Statements, and Related Documents since February this Year – 2 (Images 5 to 9)
“(7) The Command Freezing Japanese Assets on July 25”
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Document 2: C04123206200 Minister’s Instructions Regarding the Reduction of Oil Consumption (Images 1 to 4)
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On July 28, 1941, in reaction to the advance of the Japanese Army into Southern Indochina the United States government on July 25 froze Japanese assets held in the United States. Additionally all oil exports to Japan were prohibited. Following this, a perception grew within the Japanese Army that Japan was in danger of running out of resources.
For the Document 1, August 1941, portion of a notebook, created as reference material in the course of work in Division 1 of the Foreign Ministry’s American Department, contains the full text of the command freezing Japanese assets.
For Document 2, September 12, the Minister of War’s address to students, directing them to economize because of the embargo on oil and the limited emergency supplies of fuel.