According to the passage, until the bombing of Pearl Harbor, ..........

The Japanese bombing of Pearl Harbor in 1941 resulted in the immediate entry of the USA into World War II. In late 1941 more than 75 US warships were based at this base. On November 26, a Japanese force departed in secret from the Kuril Islands. Observing radio silence, it reached a launching point at 6 a.m. December 7. At 7:50 a.m., the first wave of Japanese planes struck Pearl Harbor, bombarding airfields and battleships. A second wave followed. The surprise attack was over before 10 a.m. Approximately 2,400 Americans were killed, 1,300 wounded, and 1.000 missing. Japanese losses were fewer than 100 casualties, 29 planes, and 5 submarines.