December 7, 1941, the Japanese attack on Pearl Harbor, was described by President Roosevelt as "A day which will live in infamy." The jJapanese staged a surprise air attack on naval facilities at Pearl Harbor on the Island of Oahu in Hawaii and on air force bases on the same island. It was a total surprise and sank much of the American Pacific fleet. The Japanese staged the attack because they considered war with the US inevitable and felt they had to set American war making powers back enough to allow them to seize a defensive perimeter of territories throughout the Pacific that would give them access to vital raw materials, notably petroleum and rubber.
Pearl Harbor was a huge miscalculation for the Japanese. First, they failed to bomb petroleum storage facilities at Pearl Harbor, which would have been a huge setback as the US took a year or more to rebuild supplies. Second, none of America's aircraft carriers (which turned out to be the vital sea weapons, not battleships) were in port, so they were spared. Finally, the "sneak attack" united the American people as almost nothing else could have done.