Why Was the Surprise Attack At Pearl Harbor Such a Surprise?

Lt. Cmdr. Edwin T. Layton was a worrier. And as 1941 drew to a close, Layton, the U.S. Pacific Fleet's intelligence officer, had much to worry about.

War with Japan appeared imminent, and on Dec. 1, the Japanese navy suddenly changed the radio call signs of its ships. This shift was ominous because the Communications Intelligence Unit at Pearl Harbor plotted the position of the Japanese fleet by intercepting these signals. Traffic analysts quickly identified the most commonly used new calls but were unable to locate a single Japanese aircraft carrier. Worse, none had been picked up since Nov. 25.


On Dec. 2, Layton conducted a briefing for Adm. Husband E. Kimmel, the Pacific Fleet commander, and presented him with a summary showing the approximate position of Japanese fleet units based on radio traffic. Kimmel noted that a large naval force accompanied by troopships was moving along the coast of Thailand, but there was no trace of either of the Imperial Navy's two carrier divisions.

"What!" he exclaimed. "You don't know where the carriers are?" "No, sir," replied Layton. "That's why I have 'Homeland waters' with a question mark. I don't know."


"You mean they could be coming around Diamond Head [in Hawaii], and you wouldn't know it?"

"I hope they would be sighted before now," the unhappy intelligence officer replied.

Five days later, a Japanese task forced approached undetected to within 230 miles of Hawaii and struck a devastating blow on the naval base at Pearl Harbor and nearby air bases. Surprise was complete. "Pearl Harbor was still asleep in the morning mist," one of the Japanese pilots later reported. "It was calm and serene inside the harbor, not even a trace of smoke arising from the ships . . ."

Nineteen vessels, including the entire battle line of the Pacific Fleet. were sunk or badly damaged in the worst disaster in American military history. More than 2,400 sailors, soldiers and Marines were killed -- nearly half in the explosion of the battleship Arizona. Neatly lined up as for inspection, an estimated 256 aircraft were destroyed.

The surprise at Pearl Harbor was echoed by shock and disbelief at home. Fifty years later, Americans still ask the same questions: Why wasn't Pearl Harbor on the alert? Who was responsible for failing to anticipate the attack? Was there a conspiracy to tumble the American people into a war which they did not want? Could war with Japan have been avoided?

War in the Pacific had been brewing for some time. Bogged down in a military adventure in China, the Japanese desperately needed the oil and other resources of Southeast Asia and had begun their march to the south with the seizure of French Indo-China in July 1941. American eyes were fixed, however, on the momentous events across the Atlantic, where Britain was under siege by a victorious Germany and the Soviet Union was reeling under a savage onslaught. In fact, the United States was already engaged in an undeclared war with the German U-boats which were ripping the heart of convoys carrying supplies to Britain.

President Franklin D. Roosevelt desperately wished to enter the conflict against Nazi Germany, but isolationist sentiment remained strong. And despite numerous provocations, Adolf Hitler refused to provide the incident that would unite the country in war.

In the meantime, the United States, long suspicious of what it regarded as Japan's aggressive ambitions in the Far East, froze Japanese assets and tightened an embargo on the shipment of oil and other material vital to the Japanese war machine. The Japanese military, which seized control of the government, resolved to answer the American threat with war.


War resulted from a miscalculation by Japan and the United States of the intentions of each other. Both wanted peace, but they had different definitions of what constituted peace. To the Americans, it meant a cessation of Japanese aggression in China and elsewhere; to the Japanese it meant an East Asia dominated by Japan. Surely, said the Japanese, the United State must understand that as a modern industrial nation Japan must have access to raw materials and markets. The control of Manchuria, China and Southeast Asia was absolutely essential to Japan's existence as a first-rate industrial power.

American policy, on the other hand, confused reality with morality. As a result of popular idealization of China, the United States allowed the keystone of its Far Eastern policy to be based upon a issue extraneous to its basic interests: the integrity of China. Never believing that Japan would commit national suicide by going to war with the Western powers, Roosevelt was convinced that through firmness he could force the Japanese to moderate their course. On the other hand, it is doubtful whether concessions would have placated Japan. Japanese policy had its own dynamic, and American concessions were regarded as weaknesses that invited further demands.

Japan's original strategy called for an attack on the Dutch East Indies (now Indonesia, a rich source of oil and other raw materials) with a possible strike at American bases in the Philippines to protect their flank. Once they had consolidated their conquests, they would confront the advancing Americans in a climatic sea battle in the Central Pacific. But Adm. Isoroku Yamamoto, Commander in Chief of the Combined Fleet, conceived of a much more daring plan. Having seen America's industrial might at first hand as a naval attache in Washington, he declared that Japan had no hope of winning a war with the United States "unless the U.S. Pacific Fleet in Hawaiian waters can be destroyed."

In January 1941, Yamamoto began planning a surprise air strike against the American battleships and carriers as they lay at anchor at Pearl Harbor. There was ample precedent for such a strike. Surprise was a cardinal principle of Japanese military doctrine, and such attacks had come at the beginning of wars with China and Russia. In 1932, during U.S. fleet exercises, Pearl Harbor had been successfully "raided" by carrier planes one quiet Sunday morning. And in November 1940, a handful of obsolescent British torpedo planes had devastated the Italian fleet as it lay at anchor at Taranto.

A diplomatic ballet -- designed to mask Japanese intentions -- unfolded in Tokyo and Washington as Yamamoto prepared for the attack. The Japanese navy's most experienced pilots and air crews were assigned to Plan Z -- as the operation was known -- and technicians were put to work developing armor-piercing bombs and torpedoes that would run true in the shallow waters of Pearl Harbor. Finally, on November 26, 1941, six carriers crammed with 425 planes and guarded by two battleships under the command of Vice Admiral Chichi Nagumo disappeared into the fog-shrouded North Pacific.

The following day Washington sent a "war warning" to the American commanders in the Pacific, including Kimmel and Lt. Gen. Walter C. Short, the Army commander in Hawaii, who was charged with the defense of the island. Negotiations with Japan had broken down, they were told, and an attack was expected on the Philippines, Malaya, Thailand or Borneo within the next few days. Although both commanders were ordered to execute "appropriate defensive deployment" there was nothing to indicate that Pearl Harbor was a target.


Short took no action except to mass his aircraft to prevent sabotage. Kimmel ordered a partial alert but failed to establish sustained round-the-compass aerial patrols. He considered sending the battle fleet to sea but decided to against it because the only two American carriers in the Pacific had been detached to deliver planes to the Marine garrisons on Midway and Wake islands. Torpedo nets were unavailable because the Navy Department was convinced torpedoes would be ineffective in the shallow waters of Pearl Harbor.


Smoke was still rising from the battered ships lying in the mud of Pearl Harbor when the search for scapegoats began. Short and Kimmel were relieved of their commands, yet, in vivid contrast, Gen. Douglas MacArthur escaped censure even though his forces were caught by surprise nine hours after the attack on Pearl Harbor. Obviously, the Pearl Harbor commanders were singled out as convenient scapegoats to cover inexcusable errors of commission and omission at almost every level of government.

There was plenty of blame to go around, and a cottage industry has been built on attempts to prove that Franklin Roosevelt had foreknowledge of the Japanese attack and deliberately sacrificed the Pacific Fleet to bring the United States into the war against Nazi Germany through the back door. Conspiracy theorists charge that the master plotter in the White House ignored clear signals of an impending attack on Hawaii to unite the American people behind him and then had the files sanitized to remove all traces of the conspiracy.

Pearl Harbor certainly rescued Roosevelt from an impossible dilemma, yet it is hardly likely that that he would have offered up the entire Pacific Fleet as a sacrifice when those same ships would be needed to win the war. Moreover, as far as the president was concerned, a war in the Pacific was the wrong war at the wrong time in the wrong ocean. The basic thrust of his policy was to keep Britain afloat, and a war with Japan would drain off men and material from operations against Germany, which he saw as the main enemy.

The conspiracy theory is also undermined by the lack of any assurance that even if Japan was provoked into an attack on the United States, war with Germany would result. Nothing in the Tripartite Treaty, which Japan had signed with Germany and Italy, required the signatories to come to the aid of the others in case of war. Japan used this loophole to escape joining its Axis partners in an attack on the Soviet Union, so why should Hitler assist his less-than-faithful ally?


If Hitler had not declared war on the United States following Pearl Harbor, it would have been a master stroke. There was no certainty that the American people would have called for a declaration of war against Germany, and Americans and British would have been trapped in a war in the Far East that would have divided British strength and diverted American arms and supplies from the European front.

Paradoxically, there was no shortage of intelligence about an impending war with Japan; the problem lay in the fact that there was so much information that policy-makers found it impossible to unravel Japanese intentions. Most of this intelligence was conflicting. The conventional wisdom held that the Japanese would try to seize the resources of Southeast Asia and perhaps attack the Philippines. Other analysts predicted an attack on the South Soviet Union. A Pearl Harbor attack was ruled out because it was believed the Japanese lacked the capacity to mount such an operation.

Racism had much to do with this as lack of foresight. Americans regarded the Japanese as bucktoothed, bespectacled little men, always photographing things with their ever-present cameras so they could copy them. Japanese planes and ships were said to be inferior copies of American models, myopic Japanese pilots would be unable to hit their targets and Japan's teahouse economy would quickly collapse under wartime strain. The New York tabloid PM ran an article on "How We Can Lick Japan in Sixty Days."

Information poured in upon Washington from a variety of sources. American code experts had succeeded in breaking the supposedly impregnable "Purple" diplomatic traffic between Tokyo and its emissaries in Washington. Adding to the cornucopia were messages in the lower-priority J-19 code, the tracking of Japanese naval vessels by their call signs, reports from American diplomats in Tokyo and the observed movements of Japanese troops and vessels. Random clues to the Pearl Harbor raid were embedded in this mass of information, but the volume was so overwhelming that cryptanalysts were unable to determine immediately the significant from the irrelevant.

Only later, in the brilliant light of hindsight were the relevant hints seen as heralds of a forthcoming Japanese attack. For example, not long after Admiral Yamamoto began the secret planning for the Pearl Harbor raid, Joseph C. Grew, the U.S. envoy to Japan, notified Washington that the Peruvian minister had learned "from many sources, including a Japanese source, that in the event of war breaking out between the United States and Japan, the Japanese intended to make a surprise attack against Pearl Harbor." The information was relayed to Kimmel -- with an assessment that read: "Naval Intelligence places no credence in these rumors."



"After an event a signal is always crystal clear," observes Roberta Wohlstetter in "Pearl Harbor: Warning and Decision," her account of the intelligence background of Pearl Harbor. "We can see what disaster it was signaling, since the disaster had occurred. But before the event it is obscure and pregnant with conflicting meanings . . . In short, we failed to anticipate Pearl Harbor not for want of relevant materials, but because of a plethora of irrelevant ones."

One of the major hazards of intelligence work is the tendency to rely too heavily upon a single source. Roosevelt and his associates believed that MAGIC -- the code-breaking operation reading the Japanese diplomatic code -- provided them with an infallible key to the maze of Japanese intentions. Other sources were downgraded or ignored. But Purple revealed only the information being passed on by the Foreign Office to its key representatives abroad. The most secret Japanese naval code, JN-25, in which vital naval signals were transmitted, had not been broken by the Americans. (Recently, there have been reports that the British broke JN-25 before Pearl Harbor, but Prime Minister Winston S. Churchill did not inform Roosevelt of the fact in order to tumble America into the war.)

Thus, MAGIC was a double-edged sword. While it gave American policy-makers inside knowledge of Japanese intentions, it created overconfidence. MAGIC was limited to only the president, the secretaries of State, War and Navy and few top military officers. This fetish for security was self-defeating. Neither Kimmel nor Short was privy to MAGIC, which would have allowed them to monitor the progress of the Japanese-American negotiations under way in Washington. A Purple machine was to have been sent to Pearl Harbor but it was given the British, instead.

While MAGIC was silent on the subject of Pearl Harbor, messages in J-19 betrayed an abnormal interest on the part of the Japanese consulate in Honolulu in both Pearl Harbor and the movements of the Pacific Fleet. But MAGIC had a higher priority than J-19 traffic. American decrypters devoted most of their efforts to MAGIC, and it often took up to two weeks for a J-19 dispatch to be read, translated and distributed. On Sept. 24, 1941, the Japanese consulate was instructed to divide Pearl Harbor into five alphabetically coded zones and to report the exact positions of the Pacific Fleet as the ships lay at anchor. Incredibly, no special importance was attached to this message in Washington, and it was not passed on to the commanders in Hawaii.

"I am sure that had we seen messages that had to do with Pearl Harbor, then there would have been a different evaluation of these items of intelligence," Layton, the Pacific Fleet intelligence officer, later declared. "In the late autumn of 1941, Washington was too involved with the shipping war in the Atlantic to take proper notice of intelligence related to the Pacific. Had MAGIC decrypts been available to us, they would have at least alerted us to the possibility of an attack on Pearl Harbor."

Having failed to provide Kimmel and Short with access to MAGIC, Washington was at fault for not keeping them informed of changing conditions. With war in the Pacific imminent, high-level Army and Navy officers also blundered by not making certain that the military commanders in Hawaii were on the alert. Sound military doctrine holds that a field commander should be given all pertinent information upon which to base his decision. Failing that, he should be given explicit orders. Kimmel and Short received neither.


The misuse of MAGIC lay at the heart of the Pearl Harbor disaster. There was no clearinghouse where all the raw information on Japanese intentions could be assembled, analyzed and assessed in totality.

All the individuals cleared for MAGIC had to be their own intelligence officers and make their own analyses and interpretations of the raw intelligence -- a process in which they had little or no experience. Each message represented only a single frame in a lengthy motion picture, and they never saw the entire film. Only rarely was information from one source weighed against material from another.

Had there been a sophisticated, centralized system for evaluating all the intelligence pouring in upon Roosevelt and his inner circle, the danger signals might have been separated from the surrounding noise.

William Friedman, the man who broke the Purple code, later declared that Pearl Harbor occurred because "there was nobody in either the Army or the Navy intelligence staffs in Washington whose most important, if not sole, duty was to study the whole story which the MAGIC messages were unfolding. There was no nobody whose responsibility it was to put the pieces of jigsaw puzzle together."

Nathan Miller is the author of "The Naval Air War: 1939-1945." This is another of an occaisional series of articles about World War II.