Pearl Harbor, Japanese Attack on

Pearl Harbor, Japanese Attack on


On December 7, 1941, Japanese military forces attacked the United States naval fleet anchored at Pearl Harbor on the Hawaiian island of Oahu. The surprise attack nearly devastated the American Pacific fleet. Three cruisers, three destroyers, and eight battleships along "Battleship Row" were severely damaged, and two battleships, the Oklahoma and the Arizona, were sunk. Additionally, nearly 350 American warplanes on Oahu were destroyed, virtually all that were on the ground. Over 2,400 U.S. servicemen lost their lives, and nearly 1,200 were wounded. The success of the daring attack severely impaired America's ability to check the expansion of the Japanese empire in the Pacific during the first years of WWII.

Background. As an island nation, Japan had developed a rich and complex social structure. It resisted westernization by sealing itself off from contact with the outside world, particularly Europe and the United States. By the early twentieth century, though, Japan's efforts to achieve self-sufficiency were failing, for the nation lacked its own raw materials and other resources. Some members of the ruling class argued that Japan could grow and prosper only by modernizing and adopting Western technology. Japanese nationalists, though, advocated a different path: the establishment of an empire that would not only elevate Japan's stature in the eyes of the world but also

Three U.S. battleships are hit from the air during the Japanese attack on Pearl Harbor on December 7, 1941. From left are: USS West Virginia, severly damaged; USS Tennessee, damaged; and USS Arizona, sunk. AP/WIDE WORLD PHOTOS.
Three U.S. battleships are hit from the air during the Japanese attack on Pearl Harbor on December 7, 1941. From left are: USS West Virginia , severly damaged; USS Tennessee , damaged; and USS Arizona , sunk.

guarantee access to the resources the nation needed. Moreover, many members of the nation's traditional warrior class—the Samurai—were embittered by the aftermath of World War I. Japan had backed the victorious Allies, but the Samurai believed that in the peace negotiations following the war the United States and Great Britain had treated Japan as a second-class nation. They, too, longed to assert Japan's place in world affairs.

Japan began to flex its muscles in 1931. Japanese forces stationed in Manchuria, northeast of China, to protect a Japanese railway that transported goods and raw materials out of the country suddenly seized control of all of Manchuria. Then in 1937, Japanese forces attacked the eastern provinces of China, seizing China's capital, Nanking, and the old capital, Beijing, in brutal fashion. Observers in the West were horrified by reports of the atrocities against civilians committed by Japanese invaders in the so-called "Rape of Nanking." Under the leadership of Minister of War Hideki Tojo, Japan's objective was to establish a defensive perimeter—the "Greater East Asia Co-Prosperity Sphere"—in the western Pacific. This perimeter was to extend from the Jurile Islands northeast of Japan, south to the Marianas and Marshall Islands, west through the Solomon Islands, New Guinea, and the East Indies, then northward into the Indian Ocean and southeast Asia. Tojo believed that Japan could thus drive out the Western powers, achieve a position of preeminence in East Asia, and free the nation from its dependence on Western oil, coal, rubber, ore, and other vital resources.

Tojo's strategy, however, was bringing him ever closer to conflict with those powers. The Dutch, for example, controlled the East Indies, France had a presence in Indo-China, the United States controlled the Philippines, and Malaya was a British colony. Concerned about Japanese aggression, Holland, Great Britain, and the United States imposed a trade embargo on Japan on July 26, 1941, cutting off supplies of resources to the increasingly belligerent nation. Tojo, now prime minister, was convinced that the West's goal was to starve Japan into submission.

Events came to a boil in September, 1941. United States Secretary of State Cordell Hull demanded that Japan withdraw its troops from China and Southeast Asia. While many Japanese military leaders quailed at the prospect of going to war with the United States, Tojo convinced them that acceding to American demands would be a humiliating diplomatic defeat. While carrying on protracted—and deceptive—negotiations with the United States, Japan invaded Thailand, Malaya, Burma, and the East Indies. And on November 26, the Japanese navy set sail for Pearl Harbor, where most of the U.S. Pacific fleet was docked.

The attack. Traveling under strict radio silence and screened from view by a large weather front, the Japanese battle fleet—six aircraft carriers, two battleships, two cruisers, and nine destroyers—remained undetected until it came within two hundred miles of the Hawaiian Islands. On the morning of December 7, 183 torpedo bombers and dive-bombers took off from the aircraft carriers. The Japanese pilots knew exactly where they were going because spies on the islands had given them elaborate and detailed scale models of the base, including Battleship Row. Because it was Sunday morning, most of the U.S. naval personnel were ashore, and most of the antiaircraft defenses were unmanned. At 7:49 AM local time, the attack began—and by 8:12, much of the fleet had been damaged or sunk. A second wave of bombers arrived at nine o'clock to finish what the first wave had started. In a little more than an hour, the United States fleet was severely crippled. Two days later, on December 9, the United States declared war on Japan.

Japanese espionage. The U.S. Army's Hawaii Department was charged with coastal defenses on the islands in1941. In a 1955 interview, its chief, Major General Charles D. Herron, stated, "It was a matter of common knowledge that the Japanese Consulate in Honolulu was the hotbed of espionage in Oahu." In large part, the attack on Pearl Harbor was so successful because Japanese spies, under cover of "diplomatic" posts, were able to blend easily with the large Japanese population on the islands and in the process gather valuable intelligence.

One such diplomat, for example, was Takeo Yoshikawa, who openly arrived in Hawaii by ship on March 27, 1941, as Tadashi Morimura. Yoshikawa was a trained spy assigned to the Japanese consulate on Oahu. He took a second-story room that gave him a view of Pearl Harbor and Hickam Field, where the American air fleet was based. In the weeks and months after his arrival, Yoshikawa moved freely about the island. At times he would loiter in a sugar cane field near Pearl Harbor, posing as a fieldworker. At other times he would observe Pearl Harbor from a peninsula at the end of the island or through telescopes for sightseers at a Japanese-owned restaurant on a hill overlooking the harbor. Little about his work was glamorous. He made notes, took photos, chartered small boats and planes. He even mailed back home postcards with aerial views of Pearl Harbor that helped planners construct mock-ups used to train bomber pilots for the raid. In these endeavors, he was ably supported not only by his superiors in the consular office but even by the taxi driver who frequently drove him around the island. He observed, for example, that there tended to be a large number of ships in port on Saturdays and Sundays, fewer on weekdays. He also observed American air patrols, noticing that they tended rarely to fly to the north. The kinds of details Yoshikawa meticulously noted and passed along to military planners in Japan proved invaluable on December 7, a Sunday, when Japanese planes approached Oahu from the north.

American intelligence. A question that continues to intrigue historians is how American intelligence could have failed so spectacularly, given the circumstances. The diplomatic situation was tense, and growing tenser. It was known that Germany, a Japanese ally, was pressing Japan to take action to divert American attention away from Europe. As early as January 27, 1941 Joseph Grew, the U.S. ambassador in Japan, reported to Secretary of State Hull that the embassy had learned from Japanese sources that a mass attack on Pearl Harbor was planned in case hostilities broke out. The United States had broken the Japanese diplomatic code (called Purple), so war planners from the president on down knew that spies had been reporting on the fleet deployment in Hawaii. In the weeks and days before the attack, encrypted diplomatic traffic became heavier, and increasingly ominous. On November 19, for example, American codebreakers intercepted a message from Tokyo to diplomatic posts in Washington, D.C., and several West Coast cities. The message instructed these offices to destroy all codes, coding machines, papers, and the like if they heard the words "East Wind Rain" ( Higashi No Kazeame ) in the daily weather forecast. On Thursday, December 4, the United States intercepted the so-called "winds message." Even on the morning of December 7, Army Chief of Staff General George C. Marshall sent an urgent warning to commanders in the Pacific that intercepted Japanese diplomatic messages strongly suggested an attack was imminent. Military signalmen, however, could not raise Pearl Harbor on military channels, so the message was sent by slower commercial cable. By the time it arrived, Japanese planes were in the air over Pearl Harbor.

Given this flood of intelligence, historians and military analysts question why the military failed to take steps to defend Pearl Harbor. One answer might lie in the flood of messages intercepted. Few of the hundreds of intercepted diplomatic messages specifically mentioned Pearl Harbor. Those that did—requests for information on fleet deployment at Pearl, for example—were part of general requests for similar information about numerous American bases in the Pacific. While events proved that Pearl Harbor was Japan's intended target, that seemed less apparent in 1941, when bits of unconnected intelligence arrived on the president's desk on a daily basis and no one was charged with the responsibility of "connecting the dots." Ironically, the only American official who had clear intelligence regarding Pearl Harbor was FBI director J. Edgar Hoover. The information, though, was provided by a Yugoslav double agent named Dusko Popov, who had received clear indications of Japanese intentions while operating in Germany. Hoover, though, hated Slavs, despised Popov, cut his interview with Popov short, and failed to send Popov's vital information on to the president.

Although evidence is lacking or conflicting, some revisionist historians have presented scenarios that may explain U.S. failures to protect the fleet. Some of these scenarios involve a deliberate disregard for intelligence by U.S. and British leaders on the grounds that the attack would likely force America's entrance into WWII. Most historians, however, dismiss these theories as either inconsistent with the greater body of evidence, or simply convoluted and needlessly complex explanations of normal intelligence and communications failures.



Andrew, Christopher. For the President's Eyes Only: Secret Intelligence and the American Presidency from Washington to Bush. New York: Harper Collins, 1995.

Benson, Robert Louis. A History of U.S. Communications Intelligence During World War II: Policy and Administration. Washington, D.C.: Center for Cryptologic History, National Security Agency, 1997.

Persico, Joseph E. Roosevelt's Secret War: FDR and World War II Espionage. New York: Random House, 2001.

Prange, Gordon W. At Dawn We Slept: The Untold Story of Pearl Harbor. New York: McGraw-Hill, 1981.

Winton, John. Ultra in the Pacific: How Breaking Japanese Codes & Cyphers Affected Naval Operations Against Japan: 1941–45. London: Leo Cooper, 1993.


Singh, Simon. "US Codebreakers in World War II." < > (January 9, 2003).


Cipher Machines
Codes and Ciphers
Cryptology, History
Double Agents
Purple Machine
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