Attack on Pearl Harbor

War between Japan and the United States had been a possibility that each nation had been aware of, and planned for, since the 1920s. The relationship between the two countries was cordial enough that they remained trading partners.[23][24] Tensions did not seriously grow until Japan's invasion of Manchuria in 1931. Over the next decade, Japan expanded into China, leading to the Second Sino-Japanese War in 1937. Japan spent considerable effort trying to isolate China and endeavored to secure enough independent resources to attain victory on the mainland. The "Southern Operation" was designed to assist these efforts.[25]

Pearl Harbor on October 30, 1941, looking southwest

Starting in December 1937, events such as the Japanese attack on USS Panay, the Allison incident, and the Nanking Massacre swung Western public opinion sharply against Japan. Fearing Japanese expansion,[26] the United States, United Kingdom, and France assisted China with its loans for war supply contracts.

In 1940, Japan invaded French Indochina, attempting to stymie the flow of supplies reaching China. The United States halted shipments of airplanes, parts, machine tools, and aviation gasoline to Japan, which the latter perceived as an unfriendly act.[nb 6] The United States did not stop oil exports, however, partly because of the prevailing sentiment in Washington that given Japanese dependence on American oil, such an action was likely to be considered an extreme provocation.[27][24][28]

In mid-1940, President Franklin D. Roosevelt moved the Pacific Fleet from San Diego to Hawaii.[29] He also ordered a military buildup in the Philippines, taking both actions in the hope of discouraging Japanese aggression in the Far East. Because the Japanese high command was (mistakenly) certain any attack on the United Kingdom's Southeast Asian colonies, including Singapore,[30] would bring the U.S. into the war, a devastating preventive strike appeared to be the only way to prevent American naval interference.[31] An invasion of the Philippines was also considered necessary by Japanese war planners. The U.S. War Plan Orange had envisioned defending the Philippines with an elite force of 40,000 men; this option was never implemented due to opposition from Douglas MacArthur, who felt he would need a force ten times that size. By 1941, U.S. planners expected to abandon the Philippines at the outbreak of war. Late that year, Admiral Thomas C. Hart, commander of the Asiatic Fleet, was given orders to that effect.[32]

The U.S. finally ceased oil exports to Japan in July 1941, following the seizure of French Indochina after the Fall of France, in part because of new American restrictions on domestic oil consumption.[33] Because of this decision, Japan proceeded with plans to take the oil-rich Dutch East Indies.[nb 7] On August 17, Roosevelt warned Japan that America was prepared to take opposing steps if "neighboring countries" were attacked.[35] The Japanese were faced with a dilemma—either withdraw from China and lose face, or seize new sources of raw materials in the resource-rich European colonies of Southeast Asia.

Japan and the U.S. engaged in negotiations during 1941, attempting to improve relations. In the course of these negotiations, Japan offered to withdraw from most of China and Indochina after making peace with the Nationalist government. It also proposed to adopt an independent interpretation of the Tripartite Pact and to refrain from trade discrimination, provided all other nations reciprocated. Washington rejected these proposals. Japanese Prime Minister Konoye then offered to meet with Roosevelt, but Roosevelt insisted on reaching an agreement before any meeting.[36] The U.S. ambassador to Japan repeatedly urged Roosevelt to accept the meeting, warning that it was the only way to preserve the conciliatory Konoye government and peace in the Pacific.[37] However, his recommendation was not acted upon. The Konoye government collapsed the following month, when the Japanese military rejected a withdrawal of all troops from China.[38]

Japan's final proposal, delivered on November 20, offered to withdraw from southern Indochina and to refrain from attacks in Southeast Asia, so long as the United States, United Kingdom, and Netherlands supplied one million gallons of aviation fuel, lifted their sanctions against Japan, and ceased aid to China.,[39][38] The American counter-proposal of November 26 (November 27 in Japan), the Hull note, required Japan completely evacuate China without conditions and conclude non-aggression pacts with Pacific powers. On November 26 in Japan, the day before the note's delivery, the Japanese task force left port for Pearl Harbor.

The Japanese intended the attack as a preventive action to keep the United States Pacific Fleet from interfering with its planned military actions in Southeast Asia against overseas territories of the United Kingdom, the Netherlands, and the United States. Over the course of seven hours there were coordinated Japanese attacks on the U.S.-held Philippines, Guam, and Wake Island and on the British Empire in Malaya, Singapore, and Hong Kong.[15] Additionally, from the Japanese viewpoint, it was seen as a preemptive strike "before the oil gauge ran empty."[27]

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.[40] 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.[41] Full-scale planning was underway by early spring 1941, primarily by Rear Admiral Ryūnosuke Kusaka, with assistance from Captain Minoru Genda and Yamamoto's Deputy Chief of Staff, Captain Kameto Kuroshima.[42] The planners studied the 1940 British air attack on the Italian fleet at Taranto intensively.[nb 8][nb 9]

Over the next several months, pilots were trained, equipment was adapted, and intelligence was collected. Despite these preparations, Emperor Hirohito did not approve the attack plan until November 5, after the third of four Imperial Conferences called to consider the matter.[45] 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".[46]

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, and 21% had no opinion.[47] While U.S. Pacific bases and facilities had been placed on alert on many occasions, U.S. officials doubted Pearl Harbor would be the first target; instead, they expected the Philippines would 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 to the shipment of supplies to Japan from territory to the south.[48] They also incorrectly believed that Japan was not capable of mounting more than one major naval operation at a time.[49]

The Japanese 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 and to enable Japan to conquer Southeast Asia without interference. 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.[50][51] Third, to deliver a blow to America's ability to mobilize its forces in the Pacific, battleships were chosen as the main targets, since they were the prestige ships of any navy at the time.[50] Finally, it was hoped that the attack would undermine American morale such that the U.S. government would drop its demands contrary to Japanese interests and would seek a compromise peace with Japan.[52][53]

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 was the absence from Pearl Harbor of all three of the U.S. Pacific Fleet's aircraft carriers (Enterprise, Lexington, and Saratoga). IJN top command was attached to Admiral Mahan's "decisive battle" doctrine, especially that of destroying the maximum number of battleships. Despite these concerns, Yamamoto decided to press ahead.[54]

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, were ignored, since—by their thinking—the war would be over before the influence of these facilities would be felt.[55]

Fleet submarines I-16, I-18, I-20, I-22, and I-24 each embarked a Type A midget submarine for transport to the waters off Oahu.[62] The five I-boats left Kure Naval District on November 25, 1941.[63] On December 6, they came to within 10 nmi (19 km; 12 mi) of the mouth of Pearl Harbor[64] and launched their midget subs at about 01:00 local time on December 7.[65] At 03:42 Hawaiian Time, the minesweeper Condor spotted a midget submarine periscope southwest of the Pearl Harbor entrance buoy and alerted the destroyer Ward.[66][67] The midget may have entered Pearl Harbor. However, Ward sank another midget submarine at 06:37[67][nb 10] in the first American shots in the Pacific Theater. A midget submarine on the north side of Ford Island missed the seaplane tender Curtiss with her first torpedo and missed the attacking destroyer Monaghan with her other one before being sunk by Monaghan at 08:43.[67]

A third midget submarine, Ha-19, grounded twice, once outside the harbor entrance and again on the east side of Oahu, where it was captured on December 8.[69] Ensign Kazuo Sakamaki swam ashore and was captured by Hawaii National Guard Corporal David Akui, becoming the first Japanese prisoner of war.[nb 11] A fourth had been damaged by a depth charge attack and was abandoned by its crew before it could fire its torpedoes.[70] Japanese forces received a radio message from a midget submarine at 00:41 on December 8 claiming damage to one or more large warships inside Pearl Harbor.[71]

In 1992, 2000, and 2001, Hawaii Undersea Research Laboratory's submersibles found the wreck of the fifth midget submarine lying in three parts outside Pearl Harbor. The wreck was in the debris field where much surplus U.S. equipment was dumped after the war, including vehicles and landing craft. Both of its torpedoes were missing. This correlates with reports of two torpedoes fired at the light cruiser St. Louis at 10:04 at the entrance of Pearl Harbor, and a possible torpedo fired at destroyer Helm at 08:21.[72]

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.[73] However, the attack began before the notice could be delivered. Tokyo transmitted the 5000-word notification (commonly called the "14-Part Message") in two blocks to the Japanese Embassy in Washington. Transcribing the message took too long for the Japanese ambassador to deliver it on schedule; in the event, it was not presented until more than an hour after the attack began. (In fact, U.S. code breakers had already deciphered and translated most of the message hours before he was scheduled to deliver it.)[74] The final part is sometimes described as a declaration of war. While it was viewed by a number of senior U.S government and military officials as a very strong indicator negotiations were likely to be terminated[75] and that war might break out at any moment,[76] it neither declared war nor severed diplomatic relations. A declaration of war was printed on the front page of Japan's newspapers in the evening edition of December 8 (late December 7 in the U.S.),[77] but not delivered to the U.S. government until the day after the attack.

For decades, conventional wisdom held that Japan attacked without first formally breaking diplomatic relations only because of accidents and bumbling that delayed the delivery of a document hinting at war to Washington.[78] 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, "[O]ur 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 prevailed."[79][80]

In any event, even if the Japanese had decoded and delivered the 14-Part Message before the beginning of the attack, it would not have constituted either a formal break of diplomatic relations or a declaration of war.[81] The final two paragraphs of the message read:

Thus the earnest hope of the Japanese Government to adjust Japanese-American relations and to preserve and promote the peace of the Pacific through cooperation with the American Government has finally been lost.

The Japanese Government regrets to have to notify hereby the American Government that in view of the attitude of the American Government it cannot but consider that it is impossible to reach an agreement through further negotiations.[82]

The Japanese attacked in two waves. The first wave was detected by United States Army radar at 136 nautical miles (252 km), but was misidentified as United States Army Air Forces bombers arriving from the American mainland.
Top: A: Ford Island NAS. B: Hickam Field. C: Bellows Field. D: Wheeler Field. E: Kaneohe NAS. F: Ewa MCAS. R-1: Opana Radar Station. R-2: Kawailoa RS. R-3: Kaaawa RS. G: Haleiwa. H: Kahuku. I: Wahiawa. J: Kaneohe. K: Honolulu. 0: B-17s from mainland. 1: First strike group. 1-1: Level bombers. 1–2: Torpedo bombers. 1–3: Dive bombers. 2: Second strike group. 2-1: Level bombers. 2-1F: Fighters. 2-2: Dive bombers.
Bottom: A: Wake Island. B: Midway Islands. C: Johnston Island. D: Hawaii. D-1: Oahu. 1: USS Lexington. 2: USS Enterprise. 3: First Air Fleet.

  City

  Army base

  Navy base

Attacked targets:
1: USS California
2: USS Maryland
3: USS Oklahoma
4: USS Tennessee
5: USS West Virginia
6: USS Arizona
7: USS Nevada
8: USS Pennsylvania
9: Ford Island NAS
10: Hickam field
Ignored infrastructure targets:
A: Oil storage tanks
B: CINCPAC headquarters building
C: Submarine base
D: Navy Yard

The first attack wave of 183 planes was launched north of Oahu, led by Commander Mitsuo Fuchida.[83] Six planes failed to launch due to technical difficulties.[61] The first attack included three groups of planes:[nb 12]

• 1st Group (targets: battleships and aircraft carriers)[85]
  • 49 Nakajima B5N Kate bombers armed with 800 kg (1760 lb) armor-piercing bombs, organized in four sections (1 failed to launch)
  • 40 B5N bombers armed with Type 91 torpedoes, also in four sections
• 2nd Group – (targets: Ford Island and Wheeler Field)
  • 51 Aichi D3A Val dive bombers armed with 550 lb (249 kg) general-purpose bombs (3 failed to launch)
• 3rd Group – (targets: aircraft at Ford Island, Hickam Field, Wheeler Field, Barber's Point, Kaneohe)
  • 43 Mitsubishi A6M "Zero" fighters for air control and strafing[84] (2 failed to launch)

As the first wave approached Oahu, it was detected by the U.S. Army SCR-270 radar at Opana Point near the island's northern tip. This post had been in training mode for months, but was not yet operational.[86] The operators, Privates George Elliot Jr. and Joseph Lockard, reported a target.[87] But Lieutenant Kermit A. Tyler, a newly assigned officer at the thinly manned Intercept Center, presumed it was the scheduled arrival of six B-17 bombers from California. The Japanese planes were approaching from a direction very close (only a few degrees difference) to the bombers,[88] and while the operators had never seen a formation as large on radar, they neglected to tell Tyler of its size.[89] Tyler, for security reasons, could not tell the operators of the six B-17s that were due (even though it was widely known).[89]

As the first wave planes approached Oahu, they encountered and shot down several U.S. aircraft. At least one of these radioed a somewhat incoherent warning. Other warnings from ships off the harbor entrance were still being processed or awaiting confirmation when the attacking planes began bombing and strafing. Nevertheless, it is not clear any warnings would have had much effect even if they had been interpreted correctly and much more promptly. The results the Japanese achieved in the Philippines were essentially the same as at Pearl Harbor, though MacArthur had almost nine hours warning that the Japanese had already attacked Pearl Harbor.

The air portion of the attack began at 7:48 a.m. Hawaiian Time[16] (3:18 a.m. December 8 Japanese Standard Time, as kept by ships of the Kido Butai),[90][nb 4] with the attack on Kaneohe. A total of 353[17] Japanese planes in two waves reached Oahu. Slow, vulnerable torpedo bombers led the first wave, exploiting the first moments of surprise to attack the most important ships present (the battleships), while dive bombers attacked U.S. air bases across Oahu, starting with Hickam Field, the largest, and Wheeler Field, the main U.S. Army Air Forces fighter base. The 171 planes in the second wave attacked the Army Air Forces' Bellows Field near Kaneohe on the windward side of the island and Ford Island. The only aerial opposition came from a handful of P-36 Hawks, P-40 Warhawks, and some SBD Dauntless dive bombers from the carrier Enterprise.[nb 13]

A destroyed Vindicator at Ewa field, the victim of one of the smaller attacks on the approach to Pearl Harbor

In the first wave attack, about eight of the forty-nine 800 kg (1760 lb) armor-piercing bombs dropped hit their intended battleship targets. At least two of those bombs broke up on impact, another detonated before penetrating an unarmored deck, and one was a dud. Thirteen of the forty torpedoes hit battleships, and four torpedoes hit other ships.[91] Men aboard U.S. ships awoke to the sounds of alarms, bombs exploding, and gunfire, prompting bleary-eyed men to dress as they ran to General Quarters stations. (The famous message, "Air raid Pearl Harbor. This is not drill.",[nb 14] was sent from the headquarters of Patrol Wing Two, the first senior Hawaiian command to respond.) The defenders were very unprepared. Ammunition lockers were locked, aircraft parked wingtip to wingtip in the open to prevent sabotage,[92] guns unmanned (none of the Navy's 5"/38s, only a quarter of its machine guns, and only four of 31 Army batteries got in action).[92] Despite this low alert status, many American military personnel responded effectively during the attack.[nb 15] Ensign Joseph Taussig Jr., aboard Nevada, commanded the ship's antiaircraft guns and was severely wounded but continued to be on post. Lt. Commander F. J. Thomas commanded Nevada in the captain's absence and got her under way until the ship was grounded at 9:10 a.m.[93] One of the destroyers, Aylwin, got underway with only four officers aboard, all ensigns, none with more than a year's sea duty; she operated at sea for 36 hours before her commanding officer managed to get back aboard.[94] Captain Mervyn Bennion, commanding West Virginia, led his men until he was cut down by fragments from a bomb which hit Tennessee, moored alongside.

The second planned wave consisted of 171 planes: 54 B5Ns, 81 D3As, and 36 A6Ms, commanded by Lieutenant-Commander Shigekazu Shimazaki.[84] Four planes failed to launch because of technical difficulties.[61] This wave and its targets also comprised three groups of planes:[84]

• 1st Group – 54 B5Ns armed with 550 lb (249 kg) and 132 lb (60 kg) general-purpose bombs[85]
  • 27 B5Ns – aircraft and hangars on Kaneohe, Ford Island, and Barbers Point
  • 27 B5Ns – hangars and aircraft on Hickam Field
• 2nd Group (targets: aircraft carriers and cruisers)
  • 78 D3As armed with 550 lb (249 kg) general-purpose bombs, in four sections (3 aborted)
• 3rd Group – (targets: aircraft at Ford Island, Hickam Field, Wheeler Field, Barber's Point, Kaneohe)
  • 35 A6Ms for defense and strafing (1 aborted)

The second wave was divided into three groups. One was tasked to attack Kāneʻohe, the rest Pearl Harbor proper. The separate sections arrived at the attack point almost simultaneously from several directions.

Arizona during the attack

Nevada, on fire and down at the bow, attempting to leave the harbor before being deliberately beached

West Virginia was sunk by six torpedoes and two bombs during the attack.

Ninety minutes after it began, the attack was over. 2,008 sailors were killed and 710 others wounded; 218 soldiers and airmen (who were part of the Army prior to the independent United States Air Force in 1947) were killed and 364 wounded; 109 Marines were killed and 69 wounded; and 68 civilians were killed and 35 wounded. In total, 2,403 Americans were killed, and 1,143 were wounded.[95] Eighteen ships were sunk or run aground, including five battleships.[10][96] All of the Americans killed or wounded during the attack were legally non-combatants, given that there was no state of war when the attack occurred.[21][22][97]

Of the American fatalities, nearly half were due to the explosion of Arizona's forward magazine after it was hit by a modified 16-inch (410 mm) shell.[nb 16] Author Craig Nelson wrote that the vast majority of the U.S. sailors killed at Pearl Harbor were junior enlisted personnel. "The officers of the Navy all lived in houses and the junior people were the ones on the boats, so pretty much all of the people who died in the direct line of the attack were very junior people", Nelson said. "So everyone is about 17 or 18 whose story is told there."[98]

Among the notable civilian casualties were nine Honolulu Fire Department (HFD) firefighters who responded to Hickam Field during the bombing in Honolulu, becoming the only fire department members on American soil to be attacked by a foreign power in history. Fireman Harry Tuck Lee Pang of Engine 6 was killed near the hangars by machine gun fire from a Japanese plane. Captains Thomas Macy and John Carreira of Engine 4 and Engine 1 respectively died while battling flames inside the hangar after a Japanese bomb crashed through the roof. An additional six firefighters were wounded from Japanese shrapnel. The wounded later received Purple Hearts (originally reserved for service members wounded by enemy action while partaking in armed conflicts) for their peacetime heroism that day on June 13, 1944; the three firefighters killed did not receive theirs until on December 7, 1984, at the 43rd anniversary of the attack. This made the nine men the only non-military firefighters to receive such award in U.S. history.[99]

This message denotes the first U.S. ship, St. Louis to clear Pearl Harbor. (National Archives and Records Administration) (Note that this is in answer to question "Is channel clear?" and faint writing at bottom concerning the answer being held until St. Louis had successfully cleared.)

Already damaged by a torpedo and on fire amidships, Nevada attempted to exit the harbor. She was targeted by many Japanese bombers as she got under way and sustained more hits from 250 lb (113 kg) bombs, which started further fires. She was deliberately beached to avoid blocking the harbor entrance. California was hit by two bombs and two torpedoes. The crew might have kept her afloat, but were ordered to abandon ship just as they were raising power for the pumps. Burning oil from Arizona and West Virginia drifted down on her and probably made the situation look worse than it was. The disarmed target ship Utah was holed twice by torpedoes. West Virginia was hit by seven torpedoes, the seventh tearing away her rudder. Oklahoma was hit by four torpedoes, the last two above her belt armor, which caused her to capsize. Maryland was hit by two of the converted 16" shells, but neither caused serious damage.

Although the Japanese concentrated on battleships (the largest vessels present), they did not ignore other targets. The light cruiser Helena was torpedoed, and the concussion from the blast capsized the neighboring minelayer Oglala. Two destroyers in dry dock, Cassin and Downes, were destroyed when bombs penetrated their fuel bunkers. The leaking fuel caught fire; flooding the dry dock in an effort to fight fire made the burning oil rise, and both were burned out. Cassin slipped from her keel blocks and rolled against Downes. The light cruiser Raleigh was holed by a torpedo. The light cruiser Honolulu was damaged but remained in service. The repair vessel Vestal, moored alongside Arizona, was heavily damaged and beached. The seaplane tender Curtiss was also damaged. The destroyer Shaw was badly damaged when two bombs penetrated her forward magazine.[100]

Of the 402 American aircraft in Hawaii, 188 were destroyed and 159 damaged, 155 of them on the ground.[17] Almost none were actually ready to take off to defend the base. Eight Army Air Forces pilots managed to get airborne during the attack,[101] and six were credited with downing at least one Japanese aircraft during the attack: 1st Lt. Lewis M. Sanders, 2nd Lt. Philip M. Rasmussen, 2nd Lt. Kenneth M. Taylor, 2nd Lt. George S. Welch, 2nd Lt. Harry W. Brown, and 2nd Lt. Gordon H. Sterling Jr.[102][103] Of 33 PBYs in Hawaii, 30 were destroyed and three on patrol at the time of the attack returned undamaged. Friendly fire brought down some U.S. planes on top of that, including four from an inbound flight from Enterprise.[104]

At the time of the attack, nine civilian aircraft were flying in the vicinity of Pearl Harbor. Of these, three were shot down.[105]

Fifty-five Japanese airmen and nine submariners were killed in the attack, and one, Kazuo Sakamaki, was captured. Of Japan's 414[84] available planes, 350 took part in the raid in which 29 were lost; nine in the first wave (three fighters, one dive bomber, and five torpedo bombers) and 20 in the second wave (six fighters and 14 dive bombers)[106][nb 17] with another 74 damaged by antiaircraft fire from the ground.

Several Japanese junior officers including Fuchida and Genda urged Nagumo to carry out a third strike in order to destroy as much of Pearl Harbor's fuel and torpedo[nb 18] storage, maintenance, and dry dock facilities as possible.[107] Genda, who had unsuccessfully advocated for invading Hawaii after the air attack, believed that without an invasion, three strikes were necessary to disable the base as much as possible.[108] The captains of the other five carriers in the task force reported they were willing and ready to carry out a third strike.[109] Military historians have suggested the destruction of these shore facilities would have hampered the U.S. Pacific Fleet far more seriously than the loss of its battleships.[110] If they had been wiped out, "serious [American] operations in the Pacific would have been postponed for more than a year";[111] according to Admiral Chester W. Nimitz, later Commander in Chief of the Pacific Fleet, "it would have prolonged the war another two years".[112] 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.[113]
• 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.[113]
• 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.[113] Nagumo was uncertain whether the U.S. had enough surviving planes remaining on Hawaii to launch an attack against his carriers.[114]
• 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 Royal Navy had developed night carrier techniques, so this was a substantial risk.[115]
• 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.[116]
• 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.[117] Moreover, it was Japanese Navy practice to prefer the conservation of strength over the total destruction of the enemy.[118]

At a conference aboard his flagship the following morning, Yamamoto supported Nagumo's withdrawal without launching a third wave.[117] In retrospect, sparing the vital dockyards, maintenance shops, and the oil tank farm 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.[119]

• Arizona (Rear Admiral Isaac C. Kidd's flagship of Battleship Division One): hit by four armor-piercing bombs, exploded; total loss. 1,177 dead.
• Oklahoma: hit by five torpedoes, capsized; total loss. 429 dead.
• West Virginia: hit by two bombs, seven torpedoes, sunk; returned to service July 1944. 106 dead.
• California: hit by two bombs, two torpedoes, sunk; returned to service January 1944. 100 dead.
• Nevada: hit by six bombs, one torpedo, beached; returned to service October 1942. 60 dead.
• Pennsylvania (Admiral Husband E. Kimmel's flagship of the United States Pacific Fleet):[121] in drydock with Cassin and Downes, hit by one bomb and debris from USS Cassin; remained in service. 9 dead.
• Tennessee: hit by two bombs; returned to service February 1942. 5 dead.
• Maryland: hit by two bombs; returned to service February 1942. 4 dead (including floatplane pilot shot down).

• Utah: hit by two torpedoes, capsized; total loss. 64 dead.

• Helena: hit by one torpedo; returned to service January 1942. 20 dead.
• Raleigh: hit by one torpedo; returned to service February 1942.
• Honolulu: near miss, light damage; remained in service.

• Cassin: in drydock with Downes and Pennsylvania, hit by one bomb, burned; reconstructed and returned to service February 1944.
• Downes: in drydock with Cassin and Pennsylvania, caught fire from Cassin, burned; reconstructed and returned to service November 1943.
• Helm: underway to West Loch, damaged by two near-miss bombs;[122] continued patrol; dry-docked January 15, 1942, and sailed January 20, 1942.
• Shaw: hit by 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): hit by two bombs, blast and fire from Arizona, beached; returned to service by August 1942.
• Curtiss (seaplane tender): hit by one bomb, one crashed Japanese aircraft; returned to service January 1942. 19 dead.
• Sotoyomo (harbor tug): damaged by explosion and fires in Shaw; sunk; returned to service August 1942.
• YFD-2 (yard floating dock): damaged by 250 kg bombs; sunk; returned to service January 25, 1942, servicing Shaw.

Captain Homer N. Wallin (center) supervises salvage operations aboard USS California, early 1942

Petty Officer Shigenori Nishikaichi's aircraft shown ten days after it crashed

Japanese planners of the Pearl Harbor attack had determined that some means were required for rescuing fliers whose aircraft were damaged too badly to return to the carriers. The island of Niihau, only 30 minutes flying time from Pearl Harbor, was designated as the rescue point.

The Zero flown by Petty Officer Shigenori Nishikaichi of Hiryu was damaged in the attack on Wheeler, so he flew to the rescue point. The aircraft was further damaged on landing. Nishikaichi was helped from the wreckage by one of the native Hawaiians, who, aware of the tension between the United States and Japan, took the pilot's pistol, maps, codes, and other documents. The island's residents had no telephones or radios and were completely unaware of the attack on Pearl Harbor. Nishikaichi enlisted the support of three Japanese-American residents in an attempt to recover the documents. During the ensuing struggles, Nishikaichi was killed, and a Hawaiian civilian was wounded; one collaborator committed suicide, and his wife and the third collaborator were sent to prison.

The ease with which the local ethnic Japanese residents had apparently gone to Nishikaichi's assistance was a source of concern for many and tended to support those who believed that local Japanese could not be trusted.[143]

Admiral Hara Tadaichi summed up the Japanese result by saying, "We won a great tactical victory at Pearl Harbor and thereby lost the war."[144]

While the attack accomplished its intended objective, it turned out to be largely unnecessary. Unbeknownst to Yamamoto, who conceived the original plan, the U.S. Navy had decided as far back as 1935 to abandon 'charging' across the Pacific towards the Philippines in response to an outbreak of war (in keeping with the evolution of Plan Orange).[31] The U.S. instead adopted "Plan Dog" in 1940, which emphasized keeping the IJN out of the eastern Pacific and away from the shipping lanes to Australia, while the U.S. concentrated on defeating Nazi Germany.[145]

Fortunately for the United States, the American aircraft carriers were untouched; otherwise the Pacific Fleet's ability to conduct offensive operations would have been crippled for a year or more (given no diversions from the Atlantic Fleet). As it was, the elimination of the battleships left the U.S. Navy with no choice but to rely on its aircraft carriers and submarines—the very weapons with which the U.S. Navy halted and eventually reversed the Japanese advance. While six of the eight battleships were repaired and returned to service, their relatively low speed and high fuel consumption limited their deployment, and they served mainly in shore bombardment roles (their only major action being the Battle of Surigao Strait in October 1944). A major flaw of Japanese strategic thinking was a belief that the ultimate Pacific battle would be fought by battleships, in keeping with the doctrine of Captain Alfred Thayer Mahan. As a result, Yamamoto (and his successors) hoarded battleships for a "decisive battle" that never happened.[146]

The Japanese confidence in their ability to win a quick victory meant that they neglected Pearl Harbor's navy repair yards, oil tank farms, submarine base, and old headquarters building.[55] All of these targets were omitted from Genda's list, yet they proved more important than any battleship to the American war effort in the Pacific. The survival of the repair shops and fuel depots allowed Pearl Harbor to maintain logistical support to the U.S. Navy's operations,[147][148] such as the Doolittle Raid and the Battles of Coral Sea and Midway. It was submarines that immobilized the Imperial Japanese Navy's heavy ships and brought Japan's economy to a virtual standstill by crippling the importation of oil and raw materials: by the end of 1942, the amount of raw materials brought in was cut in half, "to a disastrous ten million tons", while oil "was almost completely stopped".[nb 21] Lastly, the basement of the Old Administration Building was the home of the cryptanalytic unit which contributed significantly to the Midway ambush and the Submarine Force's success.[149]

Arizona Memorial

Ever since the Japanese attack, there has been debate as to how and why the United States had been caught unaware, and how much and when American officials knew of Japanese plans and related topics. As early as 1924, Chief of U.S. Air Service Mason Patrick displayed a concern for military vulnerabilities in the Pacific, having sent Gen. Billy Mitchell on a survey of the Pacific and the East. Patrick called Mitchell's subsequent report, which identified vulnerabilities in Hawaii, a "theoretical treatise on employment of airpower in the Pacific, which, in all probability undoubtedly will be of extreme value some 10 or 15 years hence".[150]

At least two naval war games, one in 1932 and another in 1936, proved that Pearl was vulnerable to such an attack. Admiral James Richardson was removed from command shortly after protesting President Roosevelt's decision to move the bulk of the Pacific fleet to Pearl Harbor.[151][152] The decisions of military and political leadership to ignore these warnings have contributed to conspiracy theories. Several writers, including decorated World War II veteran and journalist Robert Stinnett, author of Day of Deceit, and former United States Rear Admiral Robert Alfred Theobald, author of The Final Secret of Pearl Harbor: The Washington Background of the Pearl Harbor Attack, have argued that various parties high in the U.S. and British governments knew of the attack in advance and may even have let it happen or encouraged it in order to force the U.S. into war via the so-called "back door". However, this conspiracy theory is rejected by mainstream historians.[153][154][155][156][nb 22]