What were the causes and effects of Pearl Harbor?

Japan attacked Pearl Harbor because the US presence in the Pacific threatened Japanese goals for expansion. Ultimately, the attack on Pearl Harbor was the deciding factor in bringing the US into World War II, siding with the Allied forces and eventually ending the war with Japan through the first, and with any luck the last, use of nuclear weapons on Nagasaki and Hiroshima.

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The Japanese hoped that by crippling the US Navy with a surprise attack on Pearl Harbor, they would score a decisive victory and head off a longer war that they expected would follow. The Japanese had been steadily increasing their imperial aspirations for some time prior to this attack, and the United States had been growing increasingly worried. Concerned over growing Japanese aggression, and also in need of the same natural resources that Japan was after, the United States had placed restrictions on Japan, such as sanctioning businesses and freezing assets, in an effort to send a diplomatic message of disapproval. But Japan had no intention of scaling back its empire-building. In fact, it only planned to increase its imperialistic actions. The same day as the attack on Pearl Harbor, Japan also attacked and seized European colonies throughout the Pacific. Japanese command knew that the United States would not sit idly by and let this happen. Therefore, they hoped to destroy America's will to fight in one decisive move at Pearl Harbor.

The largest effect of this attack was to draw the United States into war with Japan. Rather than keep America out of the conflict, the attack had the opposite effect, as Americans resolved not to let this attack go unanswered. The attack on Pearl Harbor even changed the very nature of American naval combat. On the morning of the attack, the entire Pacific battleship fleet had been sitting at anchor in Pearl Harbor, and it was almost completely destroyed. However, the three aircraft carrier groups were out at sea and therefore spared. As a result, American naval tactics and strategies during WWII centered on aircraft carriers rather than battleships. Throughout the war, and continuing to this day, carriers became the focus of maritime combat rather than large battleships.

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Imperial Japan had a chronic shortage of raw materials such as oil, minerals, and steel, all of which they desperately needed to be a major economic and military power. As such raw materials could not be obtained at home, they needed to be appropriated from the countries Japan conquered as part of its aggressive territorial expansion.

But this move put the Japanese on a collision course with the United States. America also had an eye on these raw materials, and perceived Japanese territorial expansion as a strategic and economic threat.

With that in mind, the US Congress placed severe restrictions on doing business with Japan. For good measure, the Roosevelt administration seized all Japanese assets in the United States as retaliation for Imperial Japan's occupation of French Indo-China.

To some extent, the Japanese attack on Pearl Harbor can be seen as retaliation for American actions. Although the Japanese killed nearly 2,500 Americans and destroyed hundreds of planes and a large number of ships, they didn't manage to achieve any of their overriding objectives.

They didn't gain any additional raw materials, nor did they get trade and economic restrictions lifted. Instead, all they did was to bring the United States into the Second World War, thus sounding the death knell for Imperial Japan.

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Causes

One of the main causes for the attack on Pearl Harbor was Japan's ambition for expansion in the Pacific. Japan wanted to gain access to more natural resources, such as oil and steel; however, this was impossible without expanding to and conquering Southeast Asia, specifically Malaya and the Dutch East Indies. In 1949, the US president, Franklin D. Roosevelt, ordered for the US fleet to be moved from California to Pearl Harbor, which basically stopped Japan from expanding their control and influence in the Pacific.

Japan and the US stopped all economic and business collaborations, and many officials and politicians from both sides were convinced that a conflict was inevitable and all that was left was to expect an attack. Thus, on December 7th, 1941, in the hopes of weakening the US navy and gaining the upper hand, the Imperial Japanese Navy Air Service attacked the US naval base and the Pacific Fleet at Pearl Harbor.

Effects

The Japanese Army destroyed around twenty American ships (eight battleships) and more than 250 airplanes; nearly 2,500 people died, and around 1,000 people were injured. The attack is what forced America to enter the Second World War, as until then, the US was a neutral country; immediately after the attack, America declared war on Japan. Considering the damage that was caused, many think that Pearl Harbor was a successful attack; however, it was not a strategic success, as nothing changed for Japan. The country wasn't able to fulfill its aspirations to expand further in the Pacific, and the US still refused to do business with Japan.

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Short answer is: Cause= America had placed an embargo on Japan due to their increasing power and taking over most of the South Pacific islands. Japan was wanting to increase its oil for its war effort and saw the Pacific Fleet of the United States as its biggest threat.

                        Effect= You've always heard that the bombing of Pearl Harbor awoke a sleeping giant, and that it did. The United States was to remain neutral during the second war in Europe and the bombing made declaring war a popular reaction.

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A cause: Both the U.S. and Japan were establishing and expanding their imperial holdings in the Pacific at the same time.  Same place, same time, same imperial design.

A result: U.S. allied with Great Britain and Russia to defeat Hitler.

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Pearl Harbor is an American base in Hawaii.  The Japanese felt that America's involvement in the World War was inevitable.  America had already been "stern" with Japan about its expansion in the Pacific (America stopped providing valuable resources to Japan) because America had interests in the Philippines.  Japan wanted to preemptively strike so that it could cripple American forces.  It did so somewhat successfully.  The Japanese attack on Pearl Harborcaused about 2400 dead, almst 200 planes destroyed and 8 battleships destroyed or damaged. The long-term effect of Pearl Harbor was that it brought in the US to the war.  It pushed Americans into the war that they were avoiding for so long.  The Americans fought a long and hard front in the Pacific trying to avenge the attack on Pearl Harbor. 

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