How was Pearl Harbor important for victory in the Pacific?

The U.S. naval base at Pearl Harbor was the home base for the core strength of the U.S. Navy in the Pacific in early 1941. Admiral Yamamoto was the brilliant Japanese strategist who led the Imperial Japanese Navy at that time and he knew that the U.S. Pacific Fleet at Pearl Harbor was strong, but not as strong as the Japanese Navy. However, he had previously studied in the U.S. and had some familiarity with the overwhelming size, abilities, and resources of the U.S. as a country. Although the U.S. in general was not strongly prepared for war in 1941, Yamamoto knew that the U.S. could quickly build up its military. Therefore, he knew he had to do a quick, decisive knockout blow at Pearl Harbor to keep the Japanese Navy's advantage. History strongly indicates that Yamamoto was correct. The attack removed the U.S. battleships from action in the new war for many months and Japan expanded its control over the Pacific islands and southeast Asia. This was an era when battleships were still considered the most powerful and important ships. However, the U.S. aircraft carriers happened to be away from Pearl Harbor on the day of the attack. War technology was changing and it resulted in aircraft on aircraft carriers having more offensive impact than the big gun battleships. This became very evident in the Battle of Midway several months after Pearl Harbor when the U.S. aircraft carriers's planes severely damaged/sunk several Japanese aircraft carriers. This U.S. victory early in the war is considered the turning point where Japan began to lose the war.

Therefore, Pearl Harbor was crucial to Japan having a good chance to quickly overpower the larger U.S., but because the attack was not complete enough, Japan was eventually defeated. Major factors in the attack were: 1) some U.S. battleships were destroyed/sunk, but others were repaired and returned to action because repair facilities were not destroyed; 2) the aircraft carriers were missed; 3) U.S. submarines and their harbor facilities were not significantly damaged and they were a major fighting asset; 4) the huge fuel storage tanks and facilities were not destroyed; and 5) psychologically, the attack was strongly considered by Americans to be a very dishonorable "sneak" attack by a country that had apparently been claiming to be hoping for peaceful relations, and so the American population suddenly became highly motivated to do everything it could to wage successful war, which it did.