Pearl Harbor: 12 facts about the surprise attack on the US Pacific Fleet

Pearl Harbor was not the beginning of the Pacific War

Japanese forces landed in northern Malaya, then a British colony, a couple of hours before the Pearl Harbor attack; meanwhile a larger Japanese force was disembarking off neutral Thailand. What the Japanese called the Hawaiian Operation was a supporting attack; the main blow was the Southern Operation, directed against Malaya, the Philippines and the Dutch East Indies. And Japan had already been engaged in a full-scale war against China for four-and-a-half years.

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Pearl Harbor was not the Japanese response to the Hull Note

On 26 November 1941, the American secretary of state Cordell Hull had presented a note to the Japanese. This was not, as is sometimes suggested, an ultimatum; rather it was a statement of what was required for normalisation of relations. According to the note this required the withdrawal of Japanese troops from China and Indochina.

By the time of the Hull Note, Japanese forces were already in motion to carry out the Southern and Hawaiian Operations. Japanese warships of the Pearl Harbor attack force began moving to a forward base in the Kurile Islands in the north of Japan on 17 November; they sailed for Pearl Harbor on the 26th.

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The Pearl Harbor operation was an extremely difficult and risky one

It was also one of the best-planned and best-prepared operations of the Second World War. Involved was the secret passage of an entire fleet including six aircraft carriers, two battleships and three cruisers over a distance of some 3,700 miles across the North Pacific. The escorting destroyers burnt fuel oil rapidly, and refueling at sea was a new technique that could not be carried out in rough weather. If any of the Japanese ships were damaged during fighting off Hawaii it would be extremely difficult to bring them home. There were strong reasons why American military leaders thought an attack on Hawaii was impractical.

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Senior officers in the Japanese Navy opposed a full-scale Pearl Harbor attack

The operation was inspired by Admiral Yamamoto, commander-in-chief (C-in-C) of the Combined Fleet. The most important critic was an officer senior to Yamamoto; this was Admiral Nagano, the chief of the Naval General Staff. Nagano had less confidence in air power and he was wary of risking so much of the fleet in a distant operation. He was especially reluctant to risk the entire carrier force so far from Japan at a time when Japan planned attacks thousands of miles away against Malaya and the Philippines. Yamamoto demanded the use of all six big carriers, and had to threaten resignation to get a decision in his favour.

Japanese submarines were supposed to play a major role in the Pearl Harbor attack

Some 26 Japanese ‘cruiser’ submarines were concentrated around the Hawaiian Islands, their mission to pick off any American ships that survived the main air attack. In the event they achieved nothing during the main attack, although an American carrier was damaged near Hawaii in January. Five small two-man submarines, launched from larger submarines, attempted to enter the harbour early on 7 December but failed. An American destroyer sank one of the boats off the entrance to Pearl Harbor about an hour and 15 minutes before the air attack began, and nearly cost Japan the element of surprise.

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Neither in Washington nor in London were political and military leaders surprised by the outbreak of war with Japan

This, paradoxically, was a major reason for the failure of American and British intelligence to foresee the Pearl Harbor attack. Much information was gained from ‘intercepts’ of diplomatic correspondence about Japanese preparations. It was assumed these related to a move against Thailand, Malaya or the Dutch East Indies, rather than Hawaii or the Philippines.

The American commanders in the Pacific were sent a war warning on 24 November. President Franklin D Roosevelt also provided the British with informal assurances that the United States would give support if Britain and Japan went to war. There is no evidence that either President Roosevelt or Prime Minister Winston Churchill had advance warning of the Pearl Harbor attack.

The failure to patrol the approaches to Pearl Harbor was partly the result of American offensive war plans

There were a large number of US long-range aircraft in the Pacific, but they were not used to safeguard Hawaii. A force of B-17 Flying Fortress heavy bombers had been sent by the US Army to the Philippines. The 80 PBY Catalina flying boats available to the Navy were assigned to the Philippines or earmarked for offensive actions against the Japanese-held Marshall Islands.

The Pearl Harbor attack did not destroy the American Fleet

In the attack on ‘Battleship Row’ on 7 December, two elderly battleships, the Arizona and Oklahoma, were damaged beyond repair by bomb or torpedo hits. Of the 2,026 American sailors and marines killed in the attack, 1,606 had been aboard these two ships (only 218 army personnel were killed in the raid.) Three more battleships (the California, West Virginia and Nevada) sank upright in the shallow water of the harbour. They were salvaged, but two of them did not return to service until 1944 – partly because they underwent comprehensive modernisation.

Three more vessels (the Pennsylvania, Maryland and Tennessee) suffered only minor damage. They were in dry-dock or moored inboard on Battleship Row. In any event, none of the six survivors was fast enough to operate with carrier task forces in later wartime operations. The Pacific Fleet’s three aircraft carriers were away at sea on 7 December, and none of the heavy cruisers were damaged. Three modern carriers were available to the US Navy in the Atlantic, as well as two modern battleships and six older ones.

Admiral Nagumo made the correct decision when he did not mount a third attack on Pearl Harbor

The Japanese plan involved two waves of attacking planes, separated by half an hour. Nagumo, commander of the task force, was criticised for not rearming his returning aircraft and sending them back to finish off damaged American ships and oil storage tanks. But Nagumo was obeying his instructions to make a swift getaway. The attack had always been a high-risk enterprise: the elite and well-trained Japanese naval air force was limited in size, and higher losses could be expected if the Americans located the task force. Nagumo did not know where the three US Navy carriers were, nor did he know how many American planes had survived the first attacks.

The American commanders at Pearl Harbour were not scapegoats

Admiral Kimmel, C-in-C of the Pacific Fleet, and General Short, C-in-C of US Army forces on Hawaii (including air defence forces) were dismissed a few days after the attack. Some months later, the first US government enquiry found there had been dereliction of duty on the part of these two officers, and that they had made errors of judgment. Consequently, they were retired from their respective services.

Although many writers have attempted to defend Kimmel and Short, the two officers did bear responsibility for the unreadiness of the forces under their command, especially as they had been given a ‘war warning’ [on 24 November]. On the other hand, misjudgments made by superiors of Kimmel and Short in Washington did not come in for open criticism, and Admiral Bloch, a senior admiral responsible for the naval defence of Hawaii, escaped open censure. Poor coordination between the US Army and US Navy was a systemic problem, not one caused by Kimmel and Short.

Hitler’s declaration of war on the US on 11 December was not a result of Pearl Harbor

President Roosevelt suggested openly that when they attacked Pearl Harbor the Japanese had been following German instructions. In fact, Hitler and German military did not know about the proposed Pearl Harbor strike. They were, however, aware that the Japanese were preparing actions in Southeast Asia that would probably lead to war with Britain, and possibly with the US.

Under the Tripartite Pact, signed with Japan and Italy in September 1940, Germany was obliged to go to war only if the USA attacked Japan, not if Japan attacked the USA. But just before the outbreak of war the Germans secretly agreed to support the Japanese if they went to war with the USA for any reason, including a Japanese attack on American territory. President Roosevelt knew about this agreement from intercepted Japanese diplomatic correspondence. As a result, when he asked Congress for a Declaration of War on 8 December Roosevelt requested action only against Japan. In view of isolationist sentiment in the United States, the White House deemed it advisable to let the Germans make the first declaration of war, which Hitler announced in the Reichstag on 11 December. After this the president turned again to Congress and received a unanimous declaration of war against Germany and Italy.

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For Japan, Pearl Harbor was both a success and a failure

The attack did change the strategic situation. The pre-war military strategy of Britain and the US was to assemble strong forces in the west (at Singapore) and the east (at Hawaii), to deter Japan by threatening a two-front war. Pearl Harbor removed the American part of the deterrent. It made possible the rapid conquest of Malaya, the Philippines and the Dutch East Indies.

On the other hand, Admiral Yamamoto had hoped to destroy the American carrier force, and this did not happen. And by mounting a surprise attack without a declaration of war, on a Sunday morning and killing several thousand Americans, the Japanese put American public opinion totally behind the war effort.

Evan Mawdsley is professor of history at the University of Glasgow and author of December 1941: Twelve Days that Began a World War (Yale University Press, 2011).

This article was first published by HistoryExtra in December 2016