Roosevelt had wanted the U.S. to get into the war in Europe for two years before Pearl Harbor. In early July of 1941 Treasury Secretary Morganthau and Interior Secretary Ickes urged an oil embargo to thwart Japan’s expansionist policies in Southeast Asia but Roosevelt feared that would push the U.S. into “the wrong war, in the wrong ocean at the wrong time.” On July 24th the Japanese entered Southern Indochina (South Vietnam) and the U.S. responded on July 26th by freezing Japan's assets in the U.S. and, on 1 August embargoed all oil and gasoline exports to Japan. At that moment Roosevelt had to know that Japan would retaliate because 90 percent of their oil came from the U.S. He also had to know that Japan’s expansion into SE Asia endangered 90 percent of America’s vital rubber supply.Most things have a back story.
It worked! Pearl Harbor got us into the big war in a big way (not just lend lease).
Regards — Cliff