America’s relationship with Japan, a former ally and friend, was spinning out of control in the summer of 1941. The two countries were at serious odds over Japan’s conquests in China.
Increasing financial and military aid to China, the United States placed an embargo on Japan. Lacking important natural resources, the Japanese Empire needed American oil and other goods.
By the end of July, Japan had not backed down. When America cut off all oil shipments, government officials in Tokyo vowed to get their own oil - by conquering Southeast Asia.
A few weeks later, on the 18th of August (scroll down to that date on this PDF link to the Library of Congress), Congressman John Dingell of Michigan sent a letter to President Roosevelt. He had an idea which might cause Japanese officials to change their minds about Asian conquests.
What if the United States government rounded up 10,000 Japanese-Americans who lived in Hawaii? What if America incarcerated those people? Perhaps such action would ensure Japan’s “good behavior.”
Admiral Yamamoto, meanwhile, was giving serious attention to a tactical plan one of his aides - Minoru Genda - had created. The plan was to bomb Pearl Harbor.
Surprising America on December 7, 1941, Yamamoto’s men crippled the fleet at Pearl. Things could have been worse. The aircraft carriers were at sea; the fuel supplies were undamaged.
Two months later, Dingell’s suggestion took flight. The idea that America should round up her citizens of Japanese ancestry, and incarcerate them in some fashion, received the President’s blessing.
Before long, more than 112,000 people were in internment camps surrounded by watch towers and barbed wire.
Even the United States Supreme Court approved.