World War II

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Why did the Japanese choose the specific date and time for the Pearl Harbor attack?

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The Japanese chose the date and time for the attack on Pearl Harbor because they wanted to create an element of surprise. The Americans never expected any kind of attack to occur so early on a Sunday morning. The Japanese thought this was, therefore, the right time to attack, as the Americans would not be adequately prepared.

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The Japanese chose the date and time for the attack on Pearl Harbor to maximize the element of surprise and therefore maximize the damage they could inflict to the U.S. naval base in Pearl Harbor. The attack occurred on a Sunday before eight o’clock in the morning. Therefore, many of the personnel on the base were either still sleeping or were preparing to leave for church and religious services. With only a skeleton crew manning the radar and the fighter equipment, the US was at its most vulnerable, and the attack did more damage than it probably would have at a different day and time when Navy personnel were fully working and alert.

Although the base alarms went off as soon as the Japanese fighter planes were spotted, it took some time for people to mobilize and get in place to defend their ships and the base. In addition to the casualties inflicted in the attack, the surprise raid crippled or destroyed five US battleships, three Navy destroyers, seven other ships, and more than 200 naval aircraft.

Because the US crews were not prepared at that early hour, the attack managed to take out the USS Oklahoma, killing 429 crewmen who were on board the ship that morning. The USS Pennsylvania was also hit. In some ways, however, the Japanese miscalculated by choosing that date and time. There were no US aircraft carriers in the harbor that day. Moreover, the US ammunition sites were left intact even after the attack.

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Tensions between the United States and Japan had been building for a number of years prior to the attack on Pearl Harbor. The Roosevelt Administration was hostile to Imperial Japan for its increased aggression, as manifested most notably by its invasion of Manchuria. The US realized that at the current rate of expansion, Japan’s East Asian empire would represent a threat to American strategic interests in this part of the globe.

In response to Japanese imperialism, the US imposed a series of embargoes on products such as airplane parts, oil, and scrap metal. Japan was chronically short of these vital materials, and so the American government believed that these embargoes would hit the Japanese economy especially hard, making territorial expansion much more difficult.

In actual fact, however, the embargoes simply made the Japanese all the more determined to keep on expanding their empire. But in order to do this, it was inevitable that some kind of military showdown between Imperial Japan and the United States would have to take place. As Japanese armed forces were much smaller than those of the United States, the only chance the Japanese had against the Americans was by using the element of surprise. And that’s precisely what was used in the attack on Pearl Harbor, which was successful precisely because the Americans were totally unprepared for what was coming.

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While the significance of the date would only happen later, Japan attacked Pearl Harbor early on a Sunday morning because they knew that it would add to their element of surprise. They knew that the army base would still be sleeping at that early time, and most people would have the day off. By picking a day with good weather, the Japanese bombers could hit as many battleships as possible, though they missed the major target on the island: the fuel reserves. The Japanese fleet also missed the aircraft carriers that were out on maneuvers at the time. If these had been hit, it would have been harder for the United States to recover.

The attack on Pearl Harbor also fit into a larger strategy. Within days, Japan attacked the Philippines and the Aleutian Islands. The combined attack on the Pacific fleet with an ambitious campaign of aggression was meant to demonstrate Japanese strength and intimidate the United States. In reality, it only galvanized American opinion against the Axis. Japan's attack on Pearl Harbor was so unexpected that Japanese diplomats were still present in Washington that morning trying to work out a deal to get munitions. When notified of the attack, Secretary of State Cordell Hull accused the diplomats of a breach of honor even though they were not aware of the exact timing of the attack. Even though the attack on Pearl Harbor claimed over two thousand lives, it did not destroy the American fleet; actually, it was a provocation on an entire country that would fight the Axis until their unconditional surrender in 1945.

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The Japanese attacked Pearl Harbor on December 7, 1941, a Sunday, for several reasons. First, the Japanese had been expanding their empire for several years, including into China in 1937. They had signed a pact with the other Axis powers (Germany under Hitler and Italy under Mussolini), and they had taken over French Indochina in 1941. In reaction, the United States froze Japanese assets and embargoed petroleum and other products going to Japan. Hence, the Japanese wanted to retaliate against the United States. Second, the Japanese wanted the U.S. out of its way as it pursued further expansion in the Pacific.

The Japanese chose December 7 for the Pearl Harbor attack partly because it was a Sunday--a day when many of the troops would be resting or attending religious services. The first dive bomber arrived at Pearl Harbor just before 8 am, and the battleships in the harbor were open targets because the American planes were grounded at that time. A private in the U.S. Army had noticed the Japanese aircraft on his radar system, but he was told that the planes were American, as the Americans were expecting the arrival of planes. The early morning raid was also conducted on a clear day, so the weather helped the Japanese in their aims. In the attack, more than 2,300 Americans were killed, and the Pacific fleet took a large hit, as several battleships were sunk and 180 aircraft were destroyed. On December 8, 1941, the U.S. declared war on Japan, and President Franklin D. Roosevelt called the attack "a day which will live in infamy."

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