Final answer:
Japan attacked Pearl Harbor to eliminate the U.S. as a potential threat to their military expansion.
Step-by-step explanation:
Japan attacked Pearl Harbor on December 7, 1941, because they wanted to remove the U.S. as a potential threat to their planned military expansion in Southeast Asia. They believed that a surprise attack on the Pacific Fleet in Pearl Harbor would neutralize the U.S. Navy and allow Japan to conquer the territories they desired without interference.
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