Pearl Harbor

The harbor itself was not considered a serious candidate for a major base until the 1930’s, though a small naval station was established as early as 1901. Geographically, it is actually a drowned river delta within a barrier reef, shallow and with a single narrow entrance. While the latter had some advantages for antisubmarine defense, it also meant that it could take hours for the Pacific Fleet to sortie. By 1941, the harbor had extensive facilities, including dry docks, machine shops, and oil storage equal to that of the entire Japanese Empire (4.2 million barrels) — none of which were damaged in the attack. The harbor was still in the process of being dredged, but there was enough deep anchorage for a hundred warships, so long as there was no objection to anchoring them in close clusters.

By the time the war ended, oil storage at Pearl Harbor had been more than doubled, to nine million barrels.

The Pearl Harbor attack

Naval Historical Center #NH 50931

So far as the American public was concerned, the Pacific War began on 7 December 1941 with the surprise carrier attack on the naval base at Pearl Harbor. However, the Japanese Army began landing in Malaya about two hours earlier, as the opening move of their Centrifugal Offensive. These landings came as no surprise, since both British and American intelligence were tracking the movements of troop convoys south. They may have helped draw attention away from the Central Pacific and thereby contributed to the success of the Pearl Harbor strike.

The Japanese Plan. The Pearl Harbor operation was conceived by Yamamoto Isoroku, commander of Combined Fleet, which included most of the warships of the Japanese Navy. It is not known when Yamamoto first came up with the idea, but his friend and chief of staff, Fukudome Shigeru, first heard Yamamoto suggest an attack on Pearl Harbor in March or April 1940. Though opposed to a war against the United States, Yamamoto felt that if war was unavoidable then Japan's only hope was a devastating  surprise attack on the U.S. Pacific Fleet at the moment war broke out, which would allow Japan to seize and consolidate the resource-rich areas of southeast Asia and the southwest Pacific and force the Allies to accept a negotiated peace.

Yamamoto's concept was highly unorthodox. Japanese naval planning had long focused on a Great Decisive Battle to be waged between U.S. and Japanese battleships somewhere close to Japan, in the manner of the decisive Battle of Tsushima of the 1905 Russo-Japanese War. And, as a fleet commander, Yamamoto was supposed to conduct training and carry out operations planned by the Navy General Staff. But Yamamoto pressed on with conceptual study of a Pearl Harbor attack, and by December 1940, following the annual fleet maneuvers, he had decided that the operation must become part of the war plan.

Detailed planning was left to Commander Genda Minoru, the extremely talented air officer of 1 Carrier Division. Genda immediately saw the possibilities (and the challenges) of the plan, and pressed for carriers and cruisers to be the priority targets. Genda also wished to make Oahu the principle target of the Japanese opening offensive, in order to deprive the Americans of their most valuable Pacific base. However, his proposal for an amphibious assault on the island was rejected at once by Onishi and certainly would not have had the support of the Army. Genda completed a draft operational plan by February 1941.

Curiously, once the idea of seizing Oahu was rejected, Genda put no further emphasis on destroying the base itself. The target was the Pacific Fleet and its supporting air power. Nor had Yamamoto envisioned Pearl Harbor itself as a target. This oversight would have serious repercussions.

Surprise and secrecy were considered vital to the success of the attack, but there were leaks that might have proven disastrous for the Japanese if the Americans had not discounted them. On 27 January 1941, the American ambassador to Japan, Joseph Grew, sent a telegram to the State Department reporting that he had received a report from the Peruvian ambassador that the Japanese planned to attack Pearl Harbor in the event of war. Grew considered the report fantastic, and so did Navy intelligence, and nothing further was done with it. The Peruvian ambassador seems to have gotten his information from his Japanese cook, and it is unclear how the cook came by the information, assuming he had any actual knowledge. The notion of an attack on Pearl Harbor had been a cliché of Japanese writers for years before the war, and the cook may simply have been repeating the cliché.

The Japanese plan initially called for an attack by a carrier force of three fleet carriers. Following table top maneuvers on 9 October 1941, Yamaguchi, Kusaka, and Genda became convinced that all six of Japan's fleet carriers should be committed to the operation. The three officers persuaded 1 Air Fleet commander Nagumo to send Kusaka to ask the Navy chief of staff, Nagano, to approve a six-carrier strike. Nagano did so following discussions with Kusaka on 18 October. The six carriers would be able to launch two attack waves totaling over 300 aircraft against Pearl Harbor while maintaining a strong combat air patrol over their own carrier force.

Because Pearl Harbor is relatively shallow (just 40 feet deep over most of the channel,) the Americans believed that aerial torpedoes could not be successfully employed against their fleet, and the harbor was not protected by torpedo nets. However, the Japanese modified aerial torpedoes for use in the attack with wooden fins designed to ensure a shallow run. Tests showed that a bomb weighing 800 kg (1760 lbs) would penetrate battleship deck armor if dropped from an altitude of 12,000 feet (3660m). The Japanese were short of the special steel required for such weapons, but found they could convert 16" armor-piercing shells to make effective bombs. Designated the Type 99 Number 80-3, the converted bombs were streamlined to improve penetration and carried 22.8 kg (50 lbs) of high explosive. However, production was slow and only 150 of the bombs had been completed by mid-September 1941, while the last of the specially modified torpedoes were finished barely in time to be rushed to the task force rendezvous by carrier Kaga.

The aircrew were painstakingly trained for their mission. The first attack wave included a total of 89 B5N "Kate" torpedo bombers, of which 49 were configured as horizontal bombers, from Akagi, Kaga, Hiryu, and Soryu; 51 D3A "Val" dive bombers from Shokaku and Zuikaku; and 45 A6M "Zero" fighters drawn from all six carriers. The fighters and dive bombers were to attack the airfields while the torpedo and horizontal bombers were to concentrate on the carriers and battleships. The second wave consisted of 54 "Kates" from Shokaku and Zuikaku configured as horizontal bombers and 80 "Vals" and 36 "Zeros" from the other four carriers. The inexperienced torpedo bomber crews from Shokaku and Zuikaku, which had just commissioned, were given the relatively easy assignment of bombing the airfields, while the rest of the second wave were to finish off any damaged warships. The attack waves were to thoroughly wreck the largest warships and not spread their attacks, since moderately damaged vessels would be relatively easy for the Americans to salvage, and the dive bombers of the second attack wave had specific orders to wreck the exposed hulls of any capsized aircraft carriers.

In addition to the carrier strike force, the Japanese deployed a large submarine force around Oahu with orders to pick off any ships that fled Pearl Harbor. Five of these submarines carried midget submarines that were to penetrate the harbor defenses and wreak what havoc they could. This ill-advised plan accomplished nothing while nearly giving away surprise, since one of the midget submarines was detected and sunk by the destroyer Ward an hour and a half before the carrier raid conducted its first attacks. However, the report of the sinking was slow to reach higher command, and its full significance was not realized until too late. Ironically, the submarine force, which led the Japanese forces out of harbor and to war, sailed on the eleventh minute of the eleventh hour of the eleventh day of the eleventh month — the same time that the armistice went into effect ending the First World War.

To conceal their intentions, the Japanese imposed strict radio silence on Pearl Harbor Attack Force; changed their call signs on 1 December 1941, only a month after the previous change; and retransmitted old messages to maintain the impression of an unchanged volume of signals. American intelligence recognized that older signals were being retransmitted, but failed to guess their significance.

Pearl Harbor Defense. The Pearl Harbor Naval Base was under the command of Vice Admiral Claude Bloch and the Army garrison was under the command of Lieutenant General Walter Short. Short was highly regarded but seems to have been confused about his mission. His force was in Hawaii to protect the Fleet at its base, but he seems to have thought the Fleet was there to protect Hawaii and the naval base. Short also was obsessed with sabotage and less concerned with the possibility of an air raid. In fairness, the entire U.S. high command was obsessed with sabotage, since German fifth columnists had been active during the early Nazi triumphs in Europe.

Kimmel organized the Pacific Fleet operationally into three task forces under Pye, Halsey, and Brown. He was unable to keep more than one task force at sea at a time due to a shortage of oilers; the Pacific Fleet had only eleven, of which only four were equipped for underway replenishment, due to the transfer of support ships to the Atlantic. On the morning of the attack, Halsey was returning from an aircraft ferry mission to Wake with approximately half his force, while the other half was preparing to fly off aircraft to Midway. The third Pacific Fleet carrier was at San Diego for refitting, and, as a result, all three carriers of the Pacific Fleet were absent from the harbor and were spared the attack. However, Wilson was leading a small exercise at Johnston Island, leaving most of his force and almost all of Pye's force at the base.

The Attack. The encounter between Ward and the midget submarine was not the only warning the Americans missed. The Army radar sets were only being operated from 0400 to 0700, and the associated fighter direction center was not yet fully set up and its personnel were still being trained. When the radar operators at Opana Point, on the north shore of Oahu, picked up a large formation of aircraft approaching from the north just after 0700, the only officer still present at the fighter control center dismissed the sighting as a flight of American B-17s due in from the mainland. For security reasons, he did not explain this to the radar operators, and thus denied them the opportunity to report that this formation consisted of at least 50 aircraft, far more than the number of B-17s being expected.

At 0749, the Japanese air strike commander, Fuchida Mitsuo, sent out the attack signal, "To, to, to" (from the first syllable of totsugekiseyo, "charge"). This was picked up by the sensitive radio receivers of Nagato, Yamamoto's flagship in the Inland Sea. By 0753, Fuchida had sighted the harbor, saw no indications of American fighters or antiaircraft fire, and sent out the code words for success, "Tora! Tora! Tora!" ("Tiger! Tiger! Tiger!") This was received on Akagi, where even the Zen Buddhist, Kusaka, was moved to tears, and silently shook hands with Nagumo.

Because the Japanese achieved almost complete surprise, only a handful of American fighters made it off the ground, and the Army batteries around the harbor never fired a shot. This left the defense of the warships to their own antiaircraft guns, which began putting up a considerable volume of increasingly accurate fire. Unfortunately, by then the worst damage had been done. The second attack wave found the defenses alerted and the main targets obscured by smoke and fire and did relatively little damage.

Naval Historical Center #80-G-19930

American losses were very heavy. The battleships Arizona and Oklahoma were complete losses. Battleships West Virginia, California, and Nevada all settled to the bottom of the shallow harbor (the Nevada after attempting to sortie through the narrow harbor entrance) but were raised, repaired, and saw combat later in the war. Tennessee was lightly damaged in the attack itself but badly damaged by flaming oil from Arizona, while Maryland and Pennsylvania were only lightly damaged. The last three ships were fully repaired within three months of the attack.

In addition to the battleship casualties, a target ship and two destroyers were lost and three light cruisers, a destroyer, a minelayer, a repair ship, and a seaplane tender damaged. Of the 223 Army combat aircraft on Oahu, 62 were destroyed and 82 damaged. leaving just 77 combat ready. Of these, only 27 were modern fighters. The Navy lost 87 combat aircraft, most of them Catalina patrol aircraft. Personnel casualties totaled 2403 killed or missing and another 1178 wounded. Almost half of the dead were on the Arizona.

Japanese losses amounted to just 29 aircraft (9 fighters, 5 torpedo bombers, and 15 dive bombers) and 55 aircrew, in addition to the five midget submarines, none of which made it back to their mother ships. One of the midget submarine commanders was captured and become the United States' first prisoner of war.

Nagumo has been severely criticized for failing to launch additional attacks to destroy the repair facilities and oil storage around Pearl Harbor. Nimitz later estimated that the loss of the fuel oil would have lengthened the war by two years. However, Nagumo's operational orders were flawed in not designating these as priority targets in the first place. In fact, during the war game rehearsals of the attack, many of the planners stressed the importance of a quick getaway following the initial strikes. Tomioka Sadatoshi, chief of the Operations Section of Navy General Staff, had told Nagumo to get his ships home at all costs.

Nagumo was also worried about being ambushed by the missing American carriers, a fear that was not unreasonable considering what would later happen at Midway. Nor was Nagumo alone in his desire to make a quick getaway. The decision was supported by Kusaka, who had felt all along that 1 Air Fleet belonged with the main operations in Southeast Asia. Even some of the flight leaders, who were disappointed that the American carriers had not been located, wished to withdraw to prepare for a showdown with the American carrier force.

The Japanese were able to accurately estimate the damage done in their raid, both from observations during the raid itself and from a reconnaissance flight on 17 December by a seaplane from submarine I-7, which managed to scout the harbor and return safely to its mother ship.

Aftermath

Though the attack was an undoubted tactical triumph for the Japanese, it is questionable that its strategic value was worth its political cost. The old battleships lost were already in the process of being replaced with modern battleships of the North Carolina class and the majority of aircraft destroyed were obsolescent. The most grievous lost was of trained men. The Pacific Fleet was unprepared for action in the western Pacific even had it been fully intact.  During the Pearl Harbor inquiry, Admiral Kimmel testified that

... I did not think they would attack at Pearl Harbor because I did not think it was necessary for them to do so, from my point of view. We could not have materially affected their control of the waters that they wanted to control, whether or not the battleships were sunk at Pearl Harbor. In other words, I did not believe that we could move the United States Fleet to the Western Pacific until such time as auxiliaries were available, as the material condition of the ships were improved, especially with regard to anti-aircraft, and until such time as the Pacific Fleet was materially re-enforced. I thought it would be suicide for us to attempt with an inferior fleet, to move into the western Pacific.

By contrast, the Japanese had excellent facilities in French Indochina, Palau, and Formosa in close proximity to the target area. On the other hand, the attack was a severe blow to Navy morale, which did not fully recover for almost a year.

However, the attack caused the American isolationist movement to collapse overnight. On Monday, 8 December 1941, President Roosevelt gave a brief, memorable speech to Congress asking for a declaration of war, and the vote in favor was unanimous in the Senate and had only a single dissent in the House. Pearl Harbor became a battle cry for an enraged America, and guaranteed from the start that there was almost no chance of a negotiated peace with the Japanese, which was their only hope of retaining their conquests from the Centrifugal Offensive.

Responsibility for the disaster

The Japanese attack was a model of security, planning, and training, but it was still a risky plan that could have failed disastrously. That it succeeded was due in no small part to an overall climate of unpreparedness in the United States. However, the senior admiral and general on Oahu were immediately relieved of command and forced into retirement, creating an impression that they were principally responsible for the disaster. That they deserved the lion's share of the blame is arguably correct, but there was plenty of blame to go around.

Much attention has focused on the activities of American code breakers at the time of Pearl Harbor. The cryptanalysts had not yet broken the JN-25 naval operational code on 7 December 1941, but were regularly reading the machine-encrypted messages ("Purple") exchanged between the Japanese Embassy in Washington, D.C., and Tokyo. On 6 December, the cryptanalysts decoded the first thirteen parts of a 14-part message that was the Japanese government's reply to the latest statement of the American position. The 14th part arrived the next morning and was decoded just hours before the Pearl Harbor attack. The Japanese ambassadors were instructed to deliver this message to the American government at precisely 1:00 PM Washington time, corresponding to 8:00 AM in Hawaii.

The 14-part message has been characterized as a declaration of war, but it was much more ambiguous than that. The message repeated Japan's position, rejected the American position, and expressed the view that further negotiation seemed pointless. While this was certainly ominous, and its significance was not lost on the American cryptanalysts or administration, the note did not formally declare war or even present an ultimatum. Nevertheless, war warnings were sent to all Pacific commands. The message to Hawaii could not be sent by radio due to poor atmospheric conditions, and was sent as a telegram instead. However, the responsible communications officer failed to mark the telegram as urgent, and it did not reach the Hawaii commanders until the attack was long over.

The Japanese Embassy also mishandled its communications. The 14-part message was considered so sensitive that the usual embassy typists were not to be permitted to see it, and a clean copy was not ready in time for the 1:00 appointment. Tokyo had emphasized the sensitivity of the message without explaining its urgency (the Japanese ambassadors were in the dark regarding Japanese military plans, and did not themselves seem to view the message as a declaration of war) and the message was not delivered until 2:30 PM, when the attack on Pearl Harbor has been underway for almost an hour and a half. Had everything gone according to plan, the message would have been delivered at 8:00 Hawaii time, and the first wave of the Pearl Harbor attack would have arrived half an hour later. It seems likely that the Japanese would then have claimed that their "declaration of war," however ambiguous, had been delivered before opening of hostilities; but the message was delivered late, the first wave of the Pearl Harbor attack arrived early, and hostilities commenced an hour and a half before anything that could be described as a declaration of war was delivered to the American government.

The British likewise were not presented with an unambiguous declaration of war until well after the initial landings in Malaya. It was not until nearly eight hours after the Pearl Harbor attack commenced that formal declarations of war were handed to the American and British ambassadors in Tokyo.

Charges that the Roosevelt administration deliberately allowed the attack to take place, in order to draw the U.S. fully into the Second World War, began to be made almost as soon as the war ended. These charges are baseless. There is considerable evidence that Roosevelt hoped to provoke an incident that would justify a declaration of war — but in the Atlantic, against Germany, which was rightly seen by U.S. military planners as the more dangerous enemy. In hindsight, there was intelligence indicating the possibility of an attack on Pearl Harbor, but there is no credible evidence that anyone connected the dots at the time. In any case, Washington did warn the Hawaii commanders of the imminent possibility of war, and it is unclear why a successful defense of the islands against the attack would not have been as good a casus belli as the disaster that did take place. Finally, had Hitler chosen not to declare war on the U.S. after Pearl Harbor, it might have been very difficult for Roosevelt to persuade Congress to declare war on the other, more dangerous, Axis power.

References

Czarnecki et al. (accessed 25 October 2006)

Prange (1981)

Stanton (2006)

Williford and McGovern (2003)

The Pacific War Online Encyclopedia © 2007, 2009-2010 by Kent G. Budge. Index

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