The ABCD line (ABCDライン, Ēbīshīdī rain) was a series of embargoes against the Empire of Japan by foreign nations, including America, Britain, China, and the Dutch.
In 1940, in an effort to discourage Japanese militarism, these nations and others stopped selling iron ore, steel and oil to Japan, denying it the raw materials needed to continue its activities in China and French Indochina.
Faced with the possibility of economic collapse and forced withdrawal from its recent conquests, the Japanese Imperial General Headquarters began planning for a war with the Western powers in April 1941.
[5] This would result in the United States freezing Japanese assets on July 26, 1941 (alongside Britain and the Netherlands), effectively ending the export of raw materials and petroleum to Japan.
Japan would go on to occupy islands in oil-producing areas of Southeast Asia after invading the Dutch East Indies, sending over 70% of Japanese petroleum workers to rehabilitate facilities destroyed by the retreating colonial powers.