America and her allies had pretty much given Japan the complete embargo by 1939. The American's position was for Japan to completely pull out of China or no oil. Since Japan had only 2 year supply of oil in the reserves, there was only 2 strategical moves.
That's not quite the timeline of events
Chronology 1940
June 25, 1940 Japanese Warships in French Indo-China Taking advantage of the French armistice, the Japanese government demanded the right to land military forces in French Indo-China. In support of this demand, the Japanese navy dispatched warships to ports in French Indo-China.
September 4, 1940 U.S. Warning on French Indo-China Secretary of State Cordell Hull warned the Japanese government that aggressive moves against French Indo-China would have an adverse impact on American public opinion.
September 12, 1940 Japanese Warning to the U.S. U.S. Ambassador to Tokyo Joseph Grew warned Secretary of State Cordell Hull that Japan might interpret an American embargo on oil exports as sanctions and retaliate against the U.S.
September 22, 1940 Japanese Occupation of French Indo-China Japanese forces began to move into French Indo-China after the Vichy French government negotiated an agreement with the Japanese government to turn over three airfields and other concessions to the Japanese. The Japanese army then crossed the border and advanced into China 120 miles from Hanoi.
September 26, 1940 U.S. Embargo on Scrap Iron and Steel In an effort to undermine the Japanese war economy, the Roosevelt administration placed a ban on the exportation of scrap iron and steel from the United States to countries outside the Western Hemisphere (with the exception of exports to Britain), effective October 16th. The Japanese considered the policy as an act of economic warfare and declared the policy an "unfriendly act" on October 8th.
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Chronology 1941
June 25, 1941 Japanese Demands on French Indo-China. With the collapse of the French army in Europe, the Japanese government demanded that the French allow the landing of Japanese troops in French Indo-China. Japanese warships took up naval stations off Indo-Chinese ports.
July 24, 1941 Vichy French Approval of Japanese Occupation of Indo-China The Vichy French government granted the Japanese government permission to establish military control over French Indo-China. The French held tenuous administrative control over the colony.
July 26, 1941 U.S. Freezing of Japanese Credits President Franklin Roosevelt "froze" all Japanese credits in the
United States in response to the Japanese occupation of French Indo-China. The British government adopted the same policy in the United Kingdom as well. This brought American-Japanese trade to a halt. President Roosevelt placed all armed forces in the Philippines under the control of United States and assigned General Douglas MacArthur the Commander-in-Chief in the Far East. President Roosevelt also warned Japanese Ambassador Admiral Kichisaburo Nomura that additional Japanese attempts to expand Japanese military control in the Far East would force the U.S. to take immediate steps to protect American rights and interests.
October 17, 1941 Tojo Government in Japan Prince Fumumaro Konoye was forced to resign and General Hideki Tojo became the new Japanese Prime Minister and Minister of War. General Tojo was more pro-Axis in his policies.
November 20-December 7, 1941 U.S.-Japanese Negotiations in Washington To defuse the growing crisis in the Far East, Japanese delegates met with U.S. State Department officials to work out a modus vivendi. On November 20th, Japanese ambassador Admiral Nomura and special envoy Saburo Kurusu proposed that the U.S. unfreeze Japanese credits, reopen trade relations, assist Japan in the exploitation of resources in the Dutch East Indies, halt the American military build-up in the Western Pacific, and end support for the Chinese. Secretary of State Cordell Hull responded on November 26th with a proposal which called for the Japanese evacuation of French Indo-China and China, recognition of the territorial integrity of these states, extend official recognition to the Nationalist Chinese government, and conclude a multi-lateral non-aggression pact. Once the Japanese acted on these points, the U.S. would begin negotiations to establish a liberal trade policy between the two nations. Special Envoy Kurusu concluded that this proposal effectively ended the talks, but requested two weeks to study the offer. On November 29th, Secretary Hull informed the British ambassador to the U.S. that the talks had virtually collapsed. On December 1st, the Japanese government publicly rejected the Hull proposals. Despite President Franklin Roosevelt's personal message to Emperor Hirohito to use his influence to preserve the peace on December 6th, the two Japanese representatives met with Secretary Hull again on December 7th, to inform the U.S. government that the Japanese empire had severed diplomatic relations. Due to the complexity of the Japanese government instructions and the secrecy involved, the two Japanese representatives met with Secretary Hull after Washington officials learned about the surprise attack on Pearl Harbor.
December 2, 1941 Definition of Japanese Aims in Indo-China President Franklin Roosevelt asked the Japanese government for a definition of Japanese aims in French Indo-China. American trade with Japan depended on a reversal of Japanese expansionist policies in the Far East.
December 7, 1941 Japanese Attack on Pearl Harbor Japanese carrier aircraft launched a surprise attack on the U.S. Pacific Fleet, anchored at Pearl Harbor in Hawaii. Japanese forces simultaneously conducted attacks on U.S. military installations in the Philippines, Guam, Wake Island and Midway Island, as well as attacks on British military bases in Hong Kong and Malaya. The Americans, caught unprepared, lost a large number of aircraft (177) and warships, including five battleships and three cruisers at Pearl Harbor, in the attack. Over 2,340 Americans were killed plus another 876 were reported as missing. The Japanese, however, did not destroy the American aircraft carrier task forces and left the logistical infrastructure in Hawaii intact.
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Japan invaded French Indo-China to cut off some backdoor supply routes to China.
The US
only ramped up sanctions against Japan for invading French Indo-China. The oil embargo effectively started on July 26th, 1941.
