What were the causes and effects of Pearl Harbor?

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jbledbetter | High School Teacher | (Level 1) Adjunct Educator

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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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kpl1111 | High School Teacher | (Level 2) Adjunct Educator

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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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geosc | College Teacher | (Level 3) Assistant Educator

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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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crystaltu001 | Student, Grade 10 | (Level 1) Valedictorian

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The causes of the Pearl Harbor was because of rivalry between the United States and Japan. The effects of this rivalry was america dropping bombs onto Japan and Japan was nearly destroyed. Because of this, it made America go in to a war with Japan and Europe got involved too.

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zumba96 | Student, Grade 11 | (Level 3) Valedictorian

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Causes include the need of the Japanese to show they had superiority of Asia and the Pacific. They were sure that the USA would become involved in their claims in Asia, and they wanted to destroy our Navy, the 7th Fleet, based at Pearl Harbor. Our people thought the attack would be in the Philippines. 

The effects were outrage and thrust us into War in the Pacific, as well as Europe. The aforementioned rumor is fueled by a meeting between Churchill and FDR prior to this attack where Winston asked his cousin to have the USA intercede in the War in Europe. We fought in Europe for a year before we bagan our War in the Pacific.

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truthseekah | (Level 1) Salutatorian

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It is highly probable that many in the US, including the President, knew of an emminent attack on Pearl Harbor prior to Dec. 7th.

On January 27, 1941, the Peruvian envoy in Tokyo told the third secretary in the US embassy that he had learnt from intelligence sources that the Japanese had a war plan which involved an attack on Pearl Harbor. On 10 July, the US military attaché in Tokyo reported that the Japanese Navy were secretly practicing airborne torpedo attacks on targets moored in Ariake Bay-a bay that resembles Pearl Harbor. The US military attaché in Mexico also reported that the Japanese were building midget submarines which would be towed to Hawaii for an attack on Pearl Harbor.

A top British agent, codenamed 'Tricycle,' told the FBI that the Japanese planned to attack Pearl Harbor, but his information was dismissed. And a Korean agent told American broadcaster Eric Severeid that the Japanese were going to attack Pearl Harbor. The agent repeated his story to a US Senator who alerted the State Department, US Army and Navy intelligence, and President Roosevelt personally.

American intelligence had broken all the Japanese codes. On 24 September 1941, a message from Japanese Naval Intelligence headquarters in Tokyo to the Japanese consul general in Honolulu was deciphered. It requested the exact locations of all US Navy ships in Pearl Harbor. Such detailed information would only be required if the Japanese were planning an attack on the ships at their moorings. In November, another message was intercepted ordering more drills involving attacks on capital ships at anchor in preparation to 'ambush and completely destroy the US enemy.' The only American fleet within reach was at Pearl Harbor.

On 25 November, a radio message from Admiral Yamamoto ordering the Japanese task force to attack the US fleet in Hawaii was intercepted. US Intelligence was understaffed and it is not known whether this message was decoded at the time. However, that same day, the US Secretary of War, Henry Stimson, noted in his diary:

'FDR stated that we were likely to be attacked perhaps as soon as next Monday. FDR asked: 'The question was how we should maneuver them into the position of firing the first shot without too much danger to ourselves. In spite of the risk involved, however, in letting the Japanese fire the first shot, we realized that in order to have the full support of the American people it was desirable to make sure that the Japanese be the ones to do this so that there should remain no doubt in anyone's mind as to who were the aggressors.''

On 29 November, US Secretary of State Cordell Hull showed a reporter from The New York Times a message saying that Pearl Harbor was going to be attacked on 7 December. As the attack approached, the American government received information from numerous sources that 7 December would be the day. On 1 December, Naval Intelligence in San Francisco worked out from news reports and signals picked up by shipping companies that the Japanese fleet that had disappeared from home waters was then to the west of Hawaii. Those who believe that Roosevelt knew about the attack all along maintain that a number of other reports say that the Japanese would strike at Pearl Harbor, but they have yet to be declassified.


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ashley24906 | Student, Grade 11 | (Level 1) eNoter

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Japan felt they were superior to the United States and should have more territory and control. The United States was more powerful and stood in the way of them getting the resources they needed like oil and steel to establish more power. In order for them to get safe passage through the harbor to get those supplies. They had to eliminate the threat of Britain and American navy in the Pearl Harbor. So they bombed it e mobilizing them, but not for long. The United States along with some of there allies. Brought Japan down to it's knees.

The "cause" was that Japan wanted to control all of the islands of the Pacific and the U.S. Navy was considered to be an impediment to the Japanese plans. The effect of the attack of Pearl Harbor was that it forced the U.S. into a war with Japan; a war that ended in the unleashing of the worlds first, and hopefully last, use of a nuclear bomb in an attempt to defeat an enemy.

twenty-one ships of the U.S. Pacific fleet were damaged and the death toll reached 2,403, along with 68 civilians and 1,178 injured. Of the military personnel lost at Pearl Harbor, 1,177 were from the Arizona.

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veronica12398 | (Level 1) eNoter

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Pearl Harbour was run by the U.S so when Japan decided to bomb it they never realized what that would mean. It meant that the U.S would join the war and help defeat Japan and Germany. I believe it was one of the major turning points in the war. As we all know the U.S was not involved in the war until then. I believe Japan did not think the U.S would do anything to defend their country or any other country and that is where they played it wrong. With that one event they brought the biggest nation in to the war which caused the U.S to turn around a nuke Japan , and allowed the U.S to take other actions against Germany , so with one wrong call by Japan the war turned and Germany and Japan were defeated.

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jjrichardson | Student, College Freshman | (Level 1) Valedictorian

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Japan felt they were superior to the United States and should have more territory and control. The United States was more powerful and stood in the way of them getting the resources they needed like oil and steel to establish more power.Japan wanted to control all of the islands of the Pacific and the U.S. Navy was considered to be an impediment to the Japanese plans. The effect of the attack of Pearl Harbor was that it forced the U.S. into a war with .It showed America that it could be touched. America once had a huge advantage over the rest of the world in terms of a global war because it had two oceans to keep it safe. But World War II saw the end of the ocean's safety, bringing the world close

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yj24 | Student, Grade 9 | (Level 1) eNoter

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The Japanese wanted to attack Pearl Harbour to destroy the US Pacific fleet, which would pose a grave threat to Japan's ambitions in Southeast Asia. Without a US fleet to interfere (e.g. docking at Singapore/ Phillipines), japan in the short term managed stunning successes (captured Hong Kong, Malaya, Singapore, Phillipines, Java .etc).


But in the long term this was a failure as not only were the US carriers Enterprise, Yorktown and Hornet not destroyed, Japan did not hit the codebreaking station as well. Thus the US managed to further break Jap. codes, leading to the decisive defeat at Midway later.

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nt1996 | Student | (Level 1) eNoter

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There truly was no provocation to the Japanese attacks at Pearl Harbor. It was a sneak attack intended to weaken the American Naval Fleet to a point where even if America got involved, the fleet would not be able to fight at a high enough level to bring victory. This was the immediate cause of Americas involvement in the Pacific Theatre of WWII. The end result was the bombing of Hiroshima and Nagasaki. There was also a planned bombing of Tokyo, then, but that never came to fruition.


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truthseekah | (Level 1) Salutatorian

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I believe the cause of the attack was to convince the American people, who mostly believed in non-interventionalism, to go to war.  There is compelling evidence showing that US diplomacy provoked the Japanese, the attack was known ahead of time and there were many actions and non-actions by the military that were suspect, to say the least.

This article sheds light on the controversy.

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patelmilia98 | Student, Grade 9 | (Level 1) Valedictorian

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cause:Japan wanted to control all of the islands of the Pacific and US Navy was considered to be an impediment to the Japanese plans.

Effect:It forced the U.S into a war with Japan; a war that ended in the unleashing of the world's 1st, and hopefully last, the use of the nuclear bomb in an attempt to defeat an enemy.


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freshondafield | Student, Grade 9 | (Level 1) eNoter

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One of the major effects of Pearl Harbor here in the states was the camos were we kept American Japanese people during the war, fearing that they would stand up for there mother country and fight on the side were there ancestprs dwelled.  This Just shows how fear can drive a nation to treat a certain minority so horribly and show no respect.


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beartrapstrong | (Level 1) Honors

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One direct result of the attack was the overwhelming of the troops at Bataan in the Philipines. Only a few hours after the attack at pearl harbor the airfield at clark on battan was bombed. Over the next three months the american and filipinos actually destroyed an entire Japanese regiment, but the Japanese were able to send a fresh regiment. The fleet at pearl harbor were unable to come to the defense of bedraggled soldiers and 72,000 soldiers were taken prisoner. Most died of starvation in Japanese POW camps before a few were rescued 3 years later.

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