In the 1930s and preceding the attack on Pearl Harbor, Imperial Japan had a big problem: It was dependent on American oil to fuel its expansionist aspirations.
Japan invaded Manchuria in 1931. By 1937 Japan was engaged in full-scale conflict in China. Japan’s aggression and the “Rape of Nanking” shocked America. The Empire of the Sun had ruled Taiwan since 1895 and Korea since 1910.
In 1940 and 1941 Japan expanded its influence into French Indochina. Next up was to be British Malaya and the Dutch East Indies, whose oil, rubber and tin would help free Japan of dependence on America.
Japan envisioned an “Asia for Asians” free of Western meddling — ruled by Japan.
It was this grand plan that prompted Japanese thoughts of attacking Pearl Harbor; Japan wanted to keep the U.S. Pacific Fleet in Hawaii from backing up American, British and Dutch interests in Southeast Asia.
In 1941 America was focused on the Atlantic and aiding Great Britain in its war with Germany. Washington wanted to avoid conflict with Japan because U.S. armed forces at the time were prepared to handle only one front, according to Gordon W. Prange, Donald M. Goldstein and Katherine V. Dillon in “At Dawn We Slept.”
Japan imported 90 percent of its oil, with 75 to 80 percent coming from the United States. But Japan also entered into the Tripartite Pact in September 1940 — a military alliance with Nazi Germany and Fascist Italy.
The Roosevelt administration believed it could check Japan’s aggression in China and its bid for an Asian empire through trade sanctions and military deployments through 1940 and 1941, according to Jeffrey Record, a defense policy expert writing for the U.S. Army’s Strategic Studies Institute.
The United States didn’t know what Japan intended to do — but it had some insight. By the fall of 1940, U.S. cryptanalysts had broken Japanese diplomatic code and were intercepting dispatches via an effort code-named “Magic.”
Germany’s invasion of Russia in June 1941 forced Japan to review whether to move on Russia, invade south or make concessions to the United States. President Franklin D. Roosevelt, aware of the communication, characterized it as “a real drag-down and knock-out fight (to decide whether) they were going to jump-attack Russia, attack the South Seas (or) sit on the fence and be more friendly with us.”
The United States responded to Japan’s march into southern French Indochina by freezing Japanese assets in U.S. banks on July 26, 1941, effectively cutting off trade and oil. Japan predicted its fuel oil would run out in two years.
Japan found the U.S. price to turn the oil tap back on to be unacceptable: renouncing membership in the Tripartite alliance and removing military forces from China and Indochina.
The campaign of U.S. “economic warfare” against Japan, culminating with the total trade embargo in the late summer of 1941, makes sense only as a defensive measure “weakening Japan in anticipation of inevitable war,” Record writes.
He makes clear that Japan was a “serial aggressor state” that eventually brought about its own downfall. But the United States was also guilty of “grievous miscalculation.”
“U.S. attempts to deter Japanese expansion into the Southwestern Pacific via the imposition of harsh economic sanctions, redeployment of the U.S. Fleet from Southern California to Pearl Harbor, and the dispatch of B-17 long-range bombers to the Philippines all failed because the United States insisted that Japan evacuate both Indochina and China as the price for a restoration of U.S. trade,” Record wrote. “The United States demanded, in effect, that Japan abandon its empire, and by extension its aspiration to become a great power, and submit to the economic dominion of the United States — something no self-respecting Japanese leader could accept.”
