Pearl Harbor, attack on

Pearl Harbor, attack on, Japanese pre-emptive strike on the US Pacific Fleet's Hawaii base—5,500 km. (3,400 mi.) from Japan—which had been planned by the C-in-C of the Imperial Japanese Navy, Admiral Yamamoto. It was launched by units of his combined fleet at 0600 on Sunday 7 December 1941 after the Japanese realized that negotiations with the USA over, inter alia, their involvement in China (see China incident) were proving fruitless (see USA, 1).

The striking force, commanded by Vice-Admiral Nagumo, comprised two fleet and two light carriers; two carriers converted from a battleship and a cruiser; and two battleships, two cruisers, a destroyer screen, and eight support ships. They left Kure naval base between 10 and 18 November 1941, and signals deception (see signals intelligence warfare) and strict radio silence meant that the US Pacific Fleet's C-in-C, Rear-Admiral Kimmel, had no idea where the carriers were. When, on 2 December, he asked his fleet intelligence officer their location, the officer replied he did not know. ‘Do you mean to say,’ said Kimmel, ‘they could be rounding Diamond Head and you wouldn't know it?’

Kimmel's dilemma was a real one. In the event of hostilities he was required to raid the Japanese Marshall Islands, which meant he had to keep aircraft in reserve for long-range reconnaissance of them. In any case he had sufficient aircraft only to cover a 144° sector out from Hawaii. Not unnaturally he concentrated on the sector that covered the Marshall Islands—some 3,250 km. (2,000 mi.) to the south-west and the closest Japanese territory to Hawaii—as it was from them that any Japanese attack could be expected; and it was here that the only three reconnaissance aircraft aloft were patrolling at the time of the attack. But Nagumo approached from the north.

US planners in Washington were also looking the wrong way as they considered the Philippines the most likely area for a pre-emptive Japanese strike. Sabotage and submarines were thought the most likely forms of attack on Hawaii. That the navy department considered an air strike there a remote possibility was confirmed, in Kimmel's eyes at least, by its decision to transfer many of his P40 fighters to Wake and Midway islands to cover bombers being flown to reinforce the Philippines. Because the harbour lacked the necessary depth, the department had also ruled out a raid by torpedo-carrying aircraft, so no nets protected the battle fleet. In fact, the Japanese, who had learned much from the British raid on Taranto the previous year, had modified their torpedoes to run in shallow water.

On 27 November all US Army and Navy commanders had received a final war warning. But this had not mentioned Hawaii as a possible target, and the island's army commander, Lt-General Walter Short, interpreted it as meaning that any attack on Hawaii would take the form of sabotage. He therefore brought his defences to the highest state of alert for sabotage and informed Washington that he had done so. When he received no reply he assumed that he had interpreted the war warning correctly. Consequently, anti-aircraft batteries around the harbour had no ready ammunition and USAAF aircraft on the ground were easy targets as they were grouped together unarmed on airfields for easier protection against saboteurs. The naval defences, too, were alerted only to sabotage which resulted in the following state of affairs: only one in four of the navy's machine guns was manned, with the ready ammunition being locked in boxes to which only a duty officer had the keys; none of the main or 5 in. (12.7 cm.) batteries was manned; no additional long-range air reconnaissance had been ordered; and one-third of the ships' captains were ashore, as were many of their officers.

Though both Kimmel and Short were undoubtedly culpable for allowing a normal Sunday routine to continue in such circumstances, much of the blame for Hawaii's lack of general preparedness lay in Washington where inter-service and inter-departmental rivalries were rife. Hawaii's communication intelligence unit, Station Hypo, was unable to read the Japanese PURPLE diplomatic machine ciphers, the source of MAGIC intelligence, as the machine originally earmarked for it had been sent to the British government Code and Cypher School at Bletchley Park instead. Yet Washington, which also had other information about Axis interest in Pearl Harbor (see Popov), failed to supply Hawaii's commanders with this intelligence on a regular basis. Notably, it failed to supply them with deciphered messages sent to the Japanese consul general in Honolulu which requested his spies to divide Pearl Harbor into a grid of five areas and detail the ships within them. Five days later a Japanese agent working in the consulate suggested an even more detailed grid. Knowledge of these ‘bomb plot’ messages, as they came to be called, would have changed radically his estimate of the situation, Kimmel testified after the war.

By 22 November the striking force had assembled at the Kurile island of Etorofu. Four days later it sailed and under cover of a weather front (see also meteorological intelligence), which moved at about its speed across the Pacific, it was able to reach a position 450 km. (275 mi.) north of Pearl Harbor without being detected, and Nagumo then launched his aircraft. The first wave, which comprised 49 bombers, 40 torpedo bombers, 51 dive-bombers, and 43 fighters, was followed by a second wave of 54 bombers, 78 dive-bombers, and 36 fighters. As the first wave approached Hawaii the clouds parted to reveal the target. This seemed so miraculous to Nagumo and the first wave's leader that both saw in it the hand of divine intervention.

Yamamoto planned that any shipping not sunk in the air attack would be destroyed by sixteen I-type submarines, five of which carried midget submarines, and at 0645 a patrolling destroyer sank a midget submarine as it tried to enter the harbour. It had been first sighted three hours previously, but its presence was not reported until after it had been sunk. Its presence was never reported at all to the army, a typical example of the lack of inter-service co-operation and of military insouciance, which is the hallmark of the Pearl Harbor catastrophe. However, none of the submarines accomplished anything and that arm of the Japanese Navy consequently suffered a loss of prestige from which it never wholly recovered.

The first contact with the incoming waves of Japanese aircraft was made by the Opana Mobile radar Unit, whose operators were under training on Kahuku Point. Their operational hours had been extended after the war warning, from 0400 to 0700, and on that particular morning, between 0645 and 0700, all three radars picked up a reconnaissance float plane from the Japanese force. Its presence was reported but no action was taken. Then, because the breakfast truck was late, one team of operators kept their set on. This detected the approaching carrier aircraft which was also reported to the inexperienced duty officer. But, because the operators failed to report how many planes they had seen, he again did nothing as a flight of B17 bombers was expected from the same direction.

In harbour that Sunday morning were 70 warships, including 8 battleships and 24 auxiliaries, but the heavy cruisers were at sea with the fleet carriers. Guided on to this target by the music being played by a local radio station, and then by the consul general's bombing grid, the first wave of torpedo and dive bombers attacked the battle fleet, and bombed and strafed the airfields. This first phase lasted until 0825 and was followed, after a lull of fifteen minutes, by high-level bombing attacks on the harbour. Then at 0915 the dive-bombing was renewed before the raiders withdrew at 0945. Six battleships were sunk and the other two were damaged. Three destroyers, three light cruisers, and four other vessels were also sunk or damaged. On the airfields 164 planes were destroyed and another 128 damaged. Altogether, 2,403 servicemen and civilians were killed, and 1,178 wounded. Japanese combat losses were light: 29 aircraft and 6 submarines, 5 of them midgets. But Nagumo, fearing a counter-attack, made a critical mistake by refusing to launch a third wave on the harbour's repair facilities and fuel installations, which would have destroyed Pearl as a base. And though he temporarily wrecked the battle fleet, six battleships eventually returned to active service, as did all but one of the other vessels sunk or damaged. But he permanently wrecked the careers of Kimmel and Short, both of whom resigned the following spring.

Though traumatic, the disaster welded the US nation together for war as few other acts could have done. The Japanese won a significant tactical victory, but brought upon themselves a long-term strategic defeat of awesome proportions. The attack was as much a psychological shock to the USA as a physical one and no less than six wartime investigations, and one post-war Congressional inquiry, were made into the reasons for its success. None revealed the president, or any of his subordinates, guilty of misconduct and so far no evidence has ever come to light that convincingly supports the thesis that Roosevelt allowed the attack to occur in order to bring his country into the war. Nor has any incontrovertible evidence yet appeared that a British intelligence unit, the Far East Combined Bureau (FECB), was able to read the Japanese JN25 code at that time and that Churchill therefore knew about the attack beforehand. FECB files are said to have been destroyed but refutation of this canard can be found in evidence that when, in mid November 1941, the Japanese fleet ceased to transmit radio signals—and therefore could no longer be pinpointed by British radio monitors—the Joint Intelligence committee (see UK, 8) immediately informed Washington of this development. A Dutch intelligence unit at Bandung, Kamer 14, may have been able to decipher part of the code as the Dutch commander in the Far East, General Hein ter Poorten, claimed after the war that it had provided him with intelligence reports that showed Japanese naval concentrations near the Kuriles, but this remains unsubstantiated as all the Dutch files were apparently burned when the Japanese invaded Java. What seems certain is that signals dispatched before Nagumo sailed contained sufficient information to alert the Americans to the attack, as 188 deciphered after the war were connected to Japanese preparations for it (see F. Park, Cryptologia, vol. XV, October 1991).

Equally problematical is the case of what became known as the ‘East Winds’ signal. Japanese embassies had been warned that if a weather forecast, Higashi no kaze ame (east wind rain), was broadcast by Tokyo it would mean that Japanese–US relations were in danger. The potential use of this warning was known to the Americans through MAGIC intelligence and was regarded by the US navy department as being tantamount to a declaration of war if it was issued. It was later stated, though the navy department denied it, that the ‘East Winds’ message had been broadcast, and intercepted, on 4 or 5 December 1941. The message was logged but all record of it subsequently disappeared.See also Pacific war.

Bibliography

Beach, E. L. , Scapegoats: A Defense of Kimmel and Short at Pearl Harbor (Annapolis, 1995).
Prange, W. , At Dawn We Slept (New York, 1981).
Wohlstetter, R. , Pearl Harbor—Warning and Decision (Stanford, Calif., 1962).