<P> Over the next several months, pilots were trained, equipment was adapted, and intelligence was collected . Despite these preparations, Emperor Hirohito did not approve the attack plan until November 5, after the third of four Imperial Conferences called to consider the matter . Final authorization was not given by the emperor until December 1, after a majority of Japanese leaders advised him the "Hull Note" would "destroy the fruits of the China incident, endanger Manchukuo and undermine Japanese control of Korea ." </P> <P> By late 1941, many observers believed that hostilities between the U.S. and Japan were imminent . A Gallup poll just before the attack on Pearl Harbor found that 52% of Americans expected war with Japan, 27% did not, and 21% had no opinion . While U.S. Pacific bases and facilities had been placed on alert on many occasions, U.S. officials doubted Pearl Harbor would be the first target; instead, they expected the Philippines would be attacked first . This presumption was due to the threat that the air bases throughout the country and the naval base at Manila posed to sea lanes, as well as to the shipment of supplies to Japan from territory to the south . They also incorrectly believed that Japan was not capable of mounting more than one major naval operation at a time . </P> <P> The Japanese attack had several major aims . First, it intended to destroy important American fleet units, thereby preventing the Pacific Fleet from interfering with Japanese conquest of the Dutch East Indies and Malaya and to enable Japan to conquer Southeast Asia without interference . Second, it was hoped to buy time for Japan to consolidate its position and increase its naval strength before shipbuilding authorized by the 1940 Vinson - Walsh Act erased any chance of victory . Third, to deliver a blow to America's ability to mobilize its forces in the Pacific, battleships were chosen as the main targets, since they were the prestige ships of any navy at the time . Finally, it was hoped that the attack would undermine American morale such that the U.S. government would drop its demands contrary to Japanese interests, and would seek a compromise peace with Japan . </P> <P> Striking the Pacific Fleet at anchor in Pearl Harbor carried two distinct disadvantages: the targeted ships would be in very shallow water, so it would be relatively easy to salvage and possibly repair them; and most of the crews would survive the attack, since many would be on shore leave or would be rescued from the harbor . A further important disadvantage--this of timing, and known to the Japanese--was the absence from Pearl Harbor of all three of the U.S. Pacific Fleet's aircraft carriers (Enterprise, Lexington, and Saratoga). IJN top command was attached to Admiral Mahan's "decisive battle" doctrine, especially that of destroying the maximum number of battleships . Despite these concerns, Yamamoto decided to press ahead . </P>

Why did the japanese attack the united states at pearl harbor
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