The attack on Pearl Harbor

The burning wreckage of the U.S. Navy battlesh...
The burning wreckage of the U.S. Navy battleship USS Arizona (BB-39) at Pearl Harbor, Hawaii. 
The attack on Pearl Harbor (called Hawaii Operation or Operation AI[9][10] by the Japanese Imperial General Headquarters (Operation Z in planning)[11] and the Battle of Pearl Harbor[12]) was a surprise military strike conducted by the Imperial Japanese Navy against the United States naval base at Pearl Harbor, Hawaii, on the morning of December 7, 1941 (December 8 in Japan). From the standpoint of the defenders, the attack commenced at 7:48 a.m. Hawaiian Time.[13] The attack was intended as a preventive action in order to keep the U.S. Pacific Fleet from interfering with military actions the Empire of Japan was planning in Southeast Asia against overseas territories of the United Kingdom, the Netherlands, and the United States.
The base was attacked by 353[14] Japanese fighters, bombers and torpedo planes in two waves, launched from six aircraft carriers.[14] All eight U.S. Navy battleships were damaged, with four being sunk. Two of these were later raised, and with the remaining four repaired, six battleships returned to service later in the war. The Japanese also sank or damaged three cruisers, three destroyers, an anti-aircraft training ship,[nb 4] and one minelayer. 188 U.S. aircraft were destroyed; 2,402 Americans were killed[16] and 1,282 wounded. Important base installations such as the power station, shipyard, maintenance, and fuel and torpedo storage facilities, as well as the submarine piers and headquarters building (also home of the intelligence section) were not attacked. Japanese losses were light: 29 aircraft and five midget submarines lost, and 65 servicemen killed or wounded. One Japanese sailor was captured.
The attack came as a profound shock to the American people and led directly to the American entry into World War II in both the Pacific and European theaters. The following day (December 8), the United States declared war on Japan. Domestic support for non-interventionism, which had been strong,[17] disappeared. Clandestine support of Britain (for example the Neutrality Patrol) was replaced by active alliance. Subsequent operations by the U.S. prompted Germany and Italy to declare war on the U.S. on December 11, which was reciprocated by the U.S. the same day.
There were numerous historical precedents for unannounced military action by Japan. However, the lack of any formal warning, particularly while negotiations were still apparently ongoing, led President Franklin D. Roosevelt to proclaim December 7, 1941, “a date which will live in infamy“.
Anticipating war
The attack on Pearl Harbor was intended to neutralize the U.S. Pacific Fleet, and hence protect Japan’s advance into Malaya and the Dutch East Indies, where it sought access to natural resources such as oil and rubber.[3] War between Japan and the United States had been a possibility of which each nation had been aware (and developed contingency plans for) since the 1920s, though tensions did not begin to grow seriously until Japan’s 1931 invasion of Manchuria. Over the next decade, Japan continued to expand into China, leading to all-out war between those countries in 1937. Japan spent considerable effort trying to isolate China and achieve sufficient resource independence to attain victory on the mainland; the “Southern Operation” was designed to assist these efforts.[18]
From December 1937, events such as the Japanese attack on the USS Panay and the Nanking Massacre (more than 200,000 killed in indiscriminate massacres) swung public opinion in the West sharply against Japan and increased Western fear of Japanese expansion,[19] which prompted the United States, the United Kingdom, and France to provide loan assistance for war supply contracts to the Republic of China.
In 1940, Japan invaded French Indochina in an effort to control supplies reaching China. The United States halted shipments of airplanes, parts, machine tools, and aviation gasoline to Japan; this was perceived by Japan as an unfriendly act.[nb 5] The U.S. did not stop oil exports to Japan at that time in part because prevailing sentiment in Washington was that such an action would be an extreme step, given Japanese dependence on U.S. oil,[21][22] and likely to be considered a provocation by Japan.
Early in 1941, President Franklin D. Roosevelt moved the Pacific Fleet to Hawaii from its previous base in San Diego and ordered a military buildup in the Philippines in the hope of discouraging Japanese aggression in the Far East. Because the Japanese high command was (mistakenly) certain any attack on Britain’s Southeast Asian colonies would bring the U.S. into the war, a devastating preventive strike appeared to be the only way to avoid U.S. naval interference.[23] An invasion of the Philippines was also considered to be necessary by Japanese war planners. The U.S. War Plan Orange had envisioned defending the Philippines with a 40,000 man elite force. This was opposed by Douglas MacArthur, who felt that he would need a force ten times that size, and was never implemented.[24] By 1941, U.S. planners anticipated abandonment of the Philippines at the outbreak of war and orders to that effect were given in late 1941 to Admiral Thomas Hart, commander of the Asiatic Fleet.[25]
The U.S. ceased oil exports to Japan in July 1941, following Japanese expansion into French Indochina after the fall of France, in part because of new American restrictions on domestic oil consumption.[26] This in turn caused the Japanese to proceed with plans to take the Dutch East Indies, an oil-rich territory.[nb 6] The Japanese were faced with the option of either withdrawing from China and losing face or seizing and securing new sources of raw materials in the resource-rich, European-controlled colonies of South East Asia.
Preliminary planning for an attack on Pearl Harbor to protect the move into the “Southern Resource Area” (the Japanese term for the Dutch East Indies and Southeast Asia generally) had begun very early in 1941 under the auspices of Admiral Isoroku Yamamoto, then commanding Japan’s Combined Fleet.[28] He won assent to formal planning and training for an attack from the Imperial Japanese Navy General Staff only after much contention with Naval Headquarters, including a threat to resign his command.[29] Full-scale planning was underway by early spring 1941, primarily by Captain Minoru Genda.[citation needed] Japanese planning staff studied the 1940 British air attack on the Italian fleet at Taranto intensively. It was of great use to them when planning their attack on U.S. naval forces in Pearl Harbor.[nb 7][nb 8]
Over the next several months, pilots trained, equipment was adapted, and intelligence collected. Despite these preparations, the attack plan was not approved by Emperor Hirohito until November 5, after the third of four Imperial Conferences called to consider the matter.[32] Final authorization was not given by the emperor until December 1, after a majority of Japanese leaders advised him the “Hull Note” would “destroy the fruits of the China incident, endanger Manchukuo and undermine Japanese control of Korea.”[33]
By late 1941, many observers believed that hostilities between the U.S. and Japan were imminent. A Gallup poll just before the attack on Pearl Harbor found that 52% of Americans expected war with Japan, 27% did not expect war, and 21% had no opinion.[34] While U.S. Pacific bases and facilities had been placed on alert on multiple occasions, U.S. officials doubted Pearl Harbor would be the first target. They expected the Philippines to be attacked first. This presumption was due to the threat that the air bases throughout the country and the naval base at Manila posed to sea lanes, as well as the shipment of supplies to Japan from territory to the south.[35] They also incorrectly believed that Japan was not capable of mounting more than one major naval operation at a time.[36]


The attack had several major aims. First, it intended to destroy important American fleet units, thereby preventing the Pacific Fleet from interfering with Japanese conquest of the Dutch East Indies and Malaya. Second, it was hoped to buy time for Japan to consolidate its position and increase its naval strength before shipbuilding authorized by the 1940 Vinson-Walsh Act erased any chance of victory.[37][38] Finally, it was meant to deliver a severe blow to American morale, one which would discourage Americans from committing to a war extending into the western Pacific Ocean and Dutch East Indies. To maximize the effect on morale, battleships were chosen as the main targets, since they were the prestige ships of any navy at the time. The overall intention was to enable Japan to conquer Southeast Asia without interference.[37]
Striking the Pacific Fleet at anchor in Pearl Harbor carried two distinct disadvantages: the targeted ships would be in very shallow water, so it would be relatively easy to salvage and possibly repair them; and most of the crews would survive the attack, since many would be on shore leave or would be rescued from the harbor. A further important disadvantage—this of timing, and known to the Japanese—was the absence from Pearl Harbor of all three of the U.S. Pacific Fleet’s aircraft carriers (Enterprise, Lexington, and Saratoga). Ironically, the IJN top command was so imbued with Admiral Mahan‘s “decisive battle” doctrine—especially that of destroying the maximum number of battleships—that, despite these concerns, Yamamoto decided to press ahead.
Japanese confidence in their ability to achieve a short, victorious war also meant other targets in the harbor, especially the navy yard, oil tank farms, and submarine base, could safely be ignored, since—by their thinking—the war would be over before the influence of these facilities would be felt.[39]
Japanese declaration of war
The attack took place before any formal declaration of war was made by Japan, but this was not Admiral Yamamoto’s intention. He originally stipulated that the attack should not commence until thirty minutes after Japan had informed the United States that peace negotiations were at an end.[55][56] The Japanese tried to uphold the conventions of war while still achieving surprise, but the attack began before the notice could be delivered. Tokyo transmitted the 5,000-word notification (commonly called the “14-Part Message”) in two blocks to the Japanese Embassy in Washington, but transcribing the message took too long for the Japanese ambassador to deliver it in time. (In fact, U.S. code breakers had already deciphered and translated most of the message hours before he was scheduled to deliver it.)[57] The final part of the “14 Part Message” is sometimes described as a declaration of war. While it neither declared war nor severed diplomatic relations, it was viewed by a number of senior U.S government and military officials as a very strong indicator that negotiations were likely to be terminated [58] and that war might break out at any moment.[59] A declaration of war was printed on the front page of Japan’s newspapers in the evening edition of December 8,[60] but not delivered to the U.S. government until the day after the attack.
For decades, conventional wisdom held that Japan attacked without any official warning of a break in relations only because of accidents and bumbling that delayed the delivery of a document hinting at war to Washington. In 1999, however, Takeo Iguchi, a professor of law and international relations at International Christian University in Tokyo, discovered documents that pointed to a vigorous debate inside the government over how, and indeed whether, to notify Washington of Japan’s intention to break off negotiations and start a war, including a December 7 entry in the war diary saying, “our deceptive diplomacy is steadily proceeding toward success.” Of this, Iguchi said, “The diary shows that the army and navy did not want to give any proper declaration of war, or indeed prior notice even of the termination of negotiations … and they clearly pPossible third wave
Several Japanese junior officers, including Mitsuo Fuchida and Minoru Genda, the chief architect of the attack, urged Nagumo to carry out a third strike in order to destroy as much of Pearl Harbor’s fuel and torpedo[nb 19] storage, maintenance, and dry dock facilities as possible;[80] and the captains of the other five carriers in the formation reported they were willing and ready to carry out a third strike.[81] Military historians have suggested the destruction of these would have hampered the U.S. Pacific Fleet far more seriously than loss of its battleships.[82] If they had been wiped out, “serious [American] operations in the Pacific would have been postponed for more than a year”;[83] according to American Admiral Chester Nimitz, later Commander in Chief of the Pacific Fleet, “it would have prolonged the war another two years.”[84] Nagumo, however, decided to withdraw for several reasons:
  • American anti-aircraft performance had improved considerably during the second strike, and two thirds of Japan’s losses were incurred during the second wave.[85] Nagumo felt if he launched a third strike, he would be risking three quarters of the Combined Fleet’s strength to wipe out the remaining targets (which included the facilities) while suffering higher aircraft losses.[85]
  • The location of the American carriers remained unknown. In addition, the admiral was concerned his force was now within range of American land-based bombers.[85] Nagumo was uncertain whether the U.S. had enough surviving planes remaining on Hawaii to launch an attack against his carriers.[86]
  • A third wave would have required substantial preparation and turnaround time, and would have meant returning planes would have had to land at night. At the time, only the (British) Royal Navy had developed night carrier techniques, so this was a substantial risk.[87]
  • Weather had deteriorated notably since the first and second wave launching, and rough seas complicated takeoff and landing for a third wave attack.
  • The task force’s fuel situation did not permit him to remain in waters north of Pearl Harbor much longer, since he was at the very limit of logistical support. To do so risked running unacceptably low on fuel, perhaps even having to abandon destroyers en route home.[88]
  • He believed the second strike had essentially satisfied the main objective of his mission—the neutralization of the Pacific Fleet—and did not wish to risk further losses.[89] Moreover, it was Japanese Navy practice to prefer the conservation of strength over the total destruction of the enemy.[90]
At a conference aboard Yamato the following morning, Yamamoto initially supported Nagumo.[89] In retrospect, sparing the vital dockyards, maintenance shops, and oil depots meant the U.S. could respond relatively quickly to Japanese activities in the Pacific. Yamamoto later regretted Nagumo’s decision to withdraw and categorically stated it had been a great mistake not to order a third strike.[91]revailed.”[61]
Ships lost or damaged


  • Arizona: Exploded; total loss. 1,177 dead.
  • Oklahoma: Capsized, 429 dead. Refloated November 1943; capsized and lost while under tow to the mainland May 1947 [93]
  • West Virginia: two bombs, seven torpedoes, sunk; returned to service July 1944. 106 dead.
  • California: two bombs, two torpedoes, sunk; returned to service January 1944. 100 dead.
  • Nevada: six bombs, one torpedo, beached; returned to service October 1942. 60 dead.
  • Tennessee: two bombs; returned to service February 1942. 5 dead.
  • Maryland: two bombs; returned to service February 1942. 4 dead (including floatplane pilot shot down).
  • Pennsylvania (Kimmel’s Flagship):[94] in drydock with Cassin and Downes, one bomb, debris from USS Cassin; remained in service. 9 dead.

Ex-battleship (target/AA training ship)

  • Utah: Capsized; total loss. 58 dead.


  • Helena: One torpedo; returned to service January 1942. 20 dead.
  • Raleigh: One torpedo; remained in service.
  • Honolulu: Near miss, light damage; remained in service.


  • Cassin: in drydock with Downes and Pennsylvania, one bomb, burned; returned to service February 1944.
  • Downes: in drydock with Cassin and Pennsylvania, caught fire from Cassin, burned; returned to service November 1943.
  • Shaw: Three bombs; returned to service June 1942.


  • Oglala (minelayer): Damaged by torpedo hit on Helena, capsized; returned to service (as engine-repair ship) February 1944.
  • Vestal (repair ship): Two bombs, blast and fire from Arizona, beached; returned to service by August 1942.
  • Curtiss (seaplane tender): One bomb, one Japanese aircraft; returned to service January 1942. 19 dead.
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