Did American Sanctions Spur Pearl Harbor?

October 18, 2017

One hundred and thirty-three days

That’s how long the United States had to reconsider the strict sanctions it had placed on Japan in the summer of 1941. On the 134th day, Japan launched a sudden assault on the American naval base at Pearl Harbor, killing over 2,400 Americans and launching the war in the Pacific. Some criticized the decisions of the US government to involve itself in the ongoing conflict across the Pacific, but as Japan sought to gain more territory and influence, it became ever more important to halt their expansion.

Over the course of those 133 days, the American-led embargo on vital resources became intolerable to Japan, and they felt compelled to take action.

July 24th, 1941

Japanese-held territory 1942

For years, Imperial Japan had sought steady expansion throughout China and Southeast Asia, with the aim of establishing a "Co-Prosperity Sphere" under their complete control.

On July 24th, 1941, despite steady warnings from the Americans to stand down, Japan opted to increase its presence in Southeast Asia. Doing so meant forcibly taking land from several sovereign nations as well as British and Dutch colonies.

Proving that it had no intention of slowing down—in fact growing more belligerent in its expansion across Asia—Japan forced the Americans' hand. Only two days after Japan announced its decision to strengthen its position and expansion throughout Southeast Asia, President Franklin Roosevelt took action.


July 26th, 1941

Unwilling to allow Japan to go unchecked in its occupation of foreign territories, the United States imposed a series of hefty sanctions against Japan. The sanctions froze assets within the United States, resulting in the loss of three-quarters of Japan’s overseas trade. Additionally, over 80% of Japan’s imported oil supply was severed, a serious blow, especially to Japan’s Imperial Navy.

Before the imposition of the sanctions, Japan’s oil reserves were supposed to be sufficient to last three years, but with an expansion of its navy and further activity in the Pacific, that estimation would be reduced immensely.

With sanctions in place, Japan faced three options:

  1. Do nothing, and let the US cut resources vital to its expansion
  2. Continue its expansion, taking over more of Southeast Asia and getting needed resources through force
  3. Push back against the United States to remove its influence in the Pacific


Japan's answer

December 7th, 1941

134 days after the sanctions were put into place, the United States received Japan’s response in the form of a devastating attack on their Oahu naval base.

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