2017-05-23 00:49:02 UTC
The U.S. found the Japanese move provocative for a couple reasons. Most basically, the U.S. was seeking to curb and reverse Japanese expansion with lesser economic pressures, and when it did not work, total economic embargo was the only card left to play, and the U.S. was certainly unwilling to let a Japanese move on this scale go without a response.
Secondly, occupation of northern Indochina could be "justified" as a measure to gain an advantage in the China War, the Tripartite Pact could be "justified" as a measure to deter the U.S. from going to war over China rather than a measure preparatory toward wider aggression. However, southern Indochina added hardly anything to the Japanese war effort in China, rather it was most useful for further advances in the direction of Thailand, Malaya, and the DEI, and it broadened the threat to the Philippines. Therefore, to American strategists, it signaled a Japanese commitment or trajectory towards further aggression outside of China.
So, say the Japanese stand pat in northern Indochina and keep fighting in China, but they do not got south of Tonkin at all during 1941.
Assume “all else being equal” vis-à-vis Europe, rest of Asia, etc.
Would the U.S. still be letting the Japanese spend their assets in America and be letting the Japanese purchase American oil on New Years Day, 1942?
On the one hand, this should have been strategically tolerable to the U.S. because it demonstrates that previous measures had probably succeeded in arresting Japanese aggression towards the British Empire or USA. So why mess with it, or push the Japanese into a corner, when the U.S. would only be getting stronger vis-a-vis Japan during 1942, 1943 and 1944? Especially when the main American focus is against Germany, and there are hopes of making the Tripartite Pact a dead letter.
On the other hand, might other motives have made the U.S. go for the total embargo option anyway at some point between July and December 1941? For example, simply running out of patience with Japan's ongoing war with China, and an increased American consensus to show solidarity with China or boost China's morale? Or, perhaps restraint in the south by Japan could be read as Japanese intent to prepare for an assault on the Soviet Union, in cooperation with the Nazi invasion? If the Americans took this interpretation it would be logical to want to use any available economic levers to hobble such a Japanese initiative, because the Soviets surviving was seen as crucial to the chances of containing and defeating Hitler.
Poll question: No further southern expansion from June '41 on, embargo anyway by Jan '42?