Japan decided to strike before the United States fleet expanded
For Japan, a vastly expanded US Navy in the Pacific was unacceptable. A new and highly militaristic government seized power in Japan, and plans for the expansion of the empire into Southeast Asia and the South Pacific accelerated. Rather than deterring the Japanese, the placing of the American fleet at Pearl Harbor reinforced the need, in their minds, to eliminate it from the board. Japanese military planners were well aware the British could not concentrate too large a naval force in the Pacific and Indian Oceans. The Royal Australian and New Zealand Navies were of little consequence, as were the fleet units of the Dutch, defending the Dutch colonies despite the occupation of Netherlands by the Germans. Only the US Navy presented a deterrence to Japanese dominance, and the Japanese rightly considered the idea America did not want to go to war with Japan, or with anyone else.
America’s attention was drawn to the war in Europe, especially to the stirring radio broadcasts of the new British Prime Minister, Winston Churchill, who took office following the collapse of the French. Churchill painted vivid word pictures of the horrors of war at the hands of the Nazis, invoking propaganda images of the brutal Hun of the First World War. By contrast, to most Americans the Japanese were characters out of Madame Butterfly, residing in quaint paper houses with charming gardens filled with cherry blossoms and chrysanthemums. Gradually the reports of atrocities committed by the Japanese in China changed that image, at least for those paying attention. Most Americans did not. As 1941 entered its second half, Americans enjoyed newly-found prosperity, with manufacturing booming as Lend-Lease to Britain and the Soviet Union stimulated the economy. War with Japan was unthinkable.
In November 1940, Britain’s Royal Navy launched a carrier-based air raid against the main anchorage of the Italian fleet in Taranto. It was the first such strike in history, and it successfully damaged or destroyed several of Italy’s most powerful warships as they lay at anchor. The US Navy noted the success, though outside of its aviation wing the attack was largely ignored. The Japanese took a far deeper interest. The British had destroyed Italian battleships, sinking them at their moorings, using just 21 obsolescent torpedo bombers from one aircraft carrier. The harbor in which the attack took place was, like the American fleet anchorage at Pearl Harbor, relatively shallow, and protected with anti-aircraft batteries and supporting fighter aircraft. The level of success achieved by the British intrigued the Japanese planners. They proposed a similar strike, though with far more aircraft and carriers.
At the time, standard naval doctrine for aircraft carriers in all of the world’s navies were they operated in small task groups, serving the main fleets as scouts. Capable of hit and run raids, they were not viewed as lethal against capital ships. Japanese planners, led by Commander Minoru Genda, proposed massing carriers together, combining their aircraft in a coordinated strike. The Japanese plan was in essence a seaborne blitzkrieg, in which enemy air would be destroyed on the ground before additional waves of attacks demolished shipping at anchor, docks and shore facilities, and most critically, the American aircraft carriers and battleships before they could respond. Several technical issues presented difficulties to the plan. For one, the shallowness of Pearl Harbor meant aerial torpedoes would plunge to the bottom upon release from their host aircraft. Another was the lack of an aerial bomb capable of penetrating battleship armor.
The Japanese modified existing weapons to use at Pearl Harbor
In 1940 the British learned of the need to modify their aerial torpedoes for use at Taranto. The shallowness of the harbor meant they had to limit the depth to which the weapon dove upon entry into the water. Yet they could not limit it too much; to do so meant the torpedo could broach, possibly breaking up as it bounced on the surface. The Japanese studied the British solution and found, though it had worked, it was unnecessarily complex. Throughout the summer of 1941, Japanese torpedo bombers practiced attacks at Kagoshima Bay, where launched torpedoes were recovered in nets to help determine the depths to which they plunged. A long-standing myth developed from these experiments; the Japanese solved the problem through the adoption of wooden fins affixed to the rear of the torpedo. There were wooden fins, though they were there for aerial stability, not depth control.
The wooden tailfins so often cited as the key to the success of the Japanese attack were in use, in various modifications, by the British, Italian, and US Navies, and had nothing to do with resolving the issue of depth control. That was achieved through the use of active roll-control mechanisms, gyroscopically controlled, installed in the torpedoes during modifications in 1941. The wooden tailfins have long attracted interest due to the simplicity of their design, but it was the torpedo engineers who solved the problem in 1941. Before the Pearl Harbor attack, each torpedo bomber crew had the opportunity to launch a simulated strike using the modified weapons. Though several missed (as they did later in combat) enough successfully struck their target to deem the weapon a success, and its use was authorized in the attack.
The Japanese developed new bombs for use against American ships
American battleships were sufficiently armored to resist the average aerial bombs which Japanese carrier-based aircraft were capable of carrying in 1941. For example, USS Arizona’s deck armor, upon which an aerial bomb was most likely to strike, was 5 inches thick. USS Oklahoma had 4.5-inch deck armor, USS California’s was 3.5 inches thick. The bombs in Japan’s inventory at the time were incapable of penetrating the armor, which protected the ships’ vital spaces. Though they could detonate on and within the superstructure, inflicting both damage and casualties, the likelihood of the ships being rendered inoperable from aerial bombs alone was small. Japan’s planners looked to modify an existing weapon which could penetrate the armor on American battleships, inflicting fatal wounds to the massive vessels. They found such a weapon in their existing stores of 16″ armored piercing artillery shells, carried on some of their newer battleships.
The Japanese created what they designated as the Type 99 Number 80 Mark 5 bomb, a modified 1,760-pound sixteen-inch armored piercing shell. Dropped from an altitude of 10,000 feet or higher, the bomb gained enough speed during its descent to pierce almost 6 inches of armor plate. It was one such shell, dropped from a level bomber, which struck Arizona, penetrated the armor protecting its forward magazines, and caused the explosion which destroyed the ship on the morning of December 7, 1941. Another such bomb struck USS West Virginia and failed to explode, one of a number of misfires which occurred with the weapon. The catastrophic explosion of Arizona remains one of the most famous, and infamous, images of the attack on Pearl Harbor. Despite that success for the Japanese, the modified shell bomb seldom saw combat use after December 7, having proven unreliable in combat.
The United States attempted to restrain Japanese aggression through trade sanctions
In the late 1930s, Japan relied on trade with the United States to operate its economy. Over 70% of Japanese imports of scrapped steel and iron came from the United States, as well as over 90% of its copper, and more than 80% of its oil. As their aggression in Asia continued, Roosevelt squeezed its economic lifelines, gradually cutting off most of the trade between the nations. Rather than curtailing Japanese aggression, FDR’s actions led the Japanese to further their own expansion. In 1940, following the Japanese move into the French colonies of Indochina, FDR curtailed shipments of scrap metals and aviation fuels to Japan via an embargo. The United States, which then controlled the Panama Canal, closed the waterway to all Japanese ships. All the while American diplomats continued to negotiate a peaceful solution with the Japanese.
Japan responded to the closure of the canal by occupying southern Indochina, placing their troops in a position to directly threaten British interests in Burma and Singapore. It also exhibited a threat against the oil-rich Dutch East Indies. FDR, in turn, finally cut off oil exports to Japan and froze their assets in the United States. For Japan, the oil embargo made war with the United States inevitable. Though they had been rehearsing a plan for a massive carrier raid on Pearl Harbor since early 1941, they still lacked one vital element in making war, the approval of the Emperor. Negotiations with the Americans continued, but Japan refused to withdraw from China, as well as changes to its alliance with Germany and Italy, as demanded by the United States. War warnings began to appear in the Pacific in October 1941.
The Japanese attacked many facilities in addition to the Americans at Pearl Harbor
Throughout the summer and fall of 1941, American military posture in the Pacific centered around a mistaken belief. The Americans believed the Japanese were incapable of multiple major operations. Simultaneous attacks in Malaya, Burma, the Philippines, the East Indies, Wake Island, Guam, and other locations were, in the belief of American planners, impossible. Since the main focus of Japan would be to the south, a grasping of oil, tin, and rubber, that belief alone meant Pearl Harbor was safe from enemy attack. The Americans also believed the Japanese were incapable of moving a large fleet from their home islands to strike at Pearl Harbor without being detected. American radio operators and cryptographers listened to Japanese transmissions and decoded some of their diplomatic and military communications. By November 1941, these intercepts indicated an attack was imminent, somewhere in the Pacific.
In fact, the imminent attack was not somewhere in the Pacific, but seemingly everywhere in the Pacific, and in almost every instance the Japanese achieved complete surprise on December 7/8, 1941 (the Pearl Harbor attack took place on December 8 in Japan). The Japanese planned their attacks to begin coincident with an ultimatum being delivered to the Americans in Washington on December 7. In the event, the final message severing diplomatic relations arrived several hours after Pearl Harbor was attacked. The Japanese embassy would not entrust typing the document to a secretary, and the diplomat assigned to the task was not a talented typist. Thus, the Japanese attack came without warning, launched on a neutral country. Yet the Americans knew an attack was coming. The complete surprise was not the attack, but rather its location, and its devastating results.
Japan’s leadership fully supported the raid on Pearl Harbor
The Japanese attack on Pearl Harbor was a hit-and-run raid. There was no intent to invade; the Japanese goal was to inflict as much damage on the Pacific Fleet as possible and retire to the west intact. The primary targets were land-based aircraft, the aircraft carriers in the harbor, and the battleships anchored along Ford Island. If the latter were not in port, targets of opportunity were to be bombed, torpedoed, and strafed. No nation had launched a similar raid of such size, no other Navy had massed together six aircraft carriers, to operate in close coordination with each other. The overall Japanese commander, Admiral Chuichi Nagumo, had never commanded an aircraft carrier, was not a flyer and had little experience with Naval Aviation. Cautious and slow-moving, Nagumo had been a leading opponent of an attack on Pearl Harbor.
Nonetheless, his seniority assured him the command, and he relied on his aides and the captains of the six carriers to carry out the plan to his satisfaction. The Japanese practiced the attack over and over during the summer of 1941, and its operation went more or less like clockwork. One reason that it went so smoothly for the Japanese is the modest resistance they encountered from the stunned Americans at Pearl Harbor. Nearly every possible mistake which the Americans could make that day they made, some repetitively, including miscommunications, lost messages, misidentification of incoming aircraft, ignored warnings, ignored radar captures, and many more. The staff of the Pacific Fleet and the Army charged with defending the Hawaiian Islands were overwhelmed and failed to gain a modicum of control until long after the attacks were over.
The US Army and Navy shared responsibility for the defense of Pearl Harbor in 1941
In January 1941, Secretary of the Navy Frank Knox wrote to Secretary of War Henry L. Stimson, “If war eventuates with Japan, it is believed easily possible that hostilities would be initiated by a surprise attack upon the fleet or the naval base at Pearl Harbor”. Knox went on to identify defenses against air attack, which he deemed “probable”, as inadequate. Knox urged coordination and cooperation between the Navy and Army to defend the installations, though the defense of the island was entirely the responsibility of the Army. Stimson forwarded the letter, with an endorsement supporting its recommendations, to Admiral Husband Kimmel, Commander in Chief Pacific Fleet, and General Walter Short, Commander of the Army’s Hawaiian Department. Through his actions, it was evident Short did not concur with Knox’s assessment of the situation in Hawaii.
Short believed the greatest danger faced by the US Army Air Forces on the Hawaiian Islands came from potential saboteurs, rather than the Japanese Navy. In order to protect his airplanes from sabotage, he ordered them parked in rows on the airfields, wingtip to wingtip, rather than dispersed to protect them from aerial attacks. Short received several war warnings in the week leading up to December 7. In his post-attack defense, he claimed the warnings were vague and did not specifically tell him what to do. He also blamed Navy reconnaissance for not providing him with adequate warnings of Japanese activities. When the Japanese attacked, most of the airplanes the Americans lost that day were destroyed on the ground, the neat rows providing easy targets for the attacking Japanese. The Army relieved Short of his command on December 17, 1941.
The Japanese never considered an invasion of Hawaii in December 1941
During the planning phase for the Pearl Harbor attack, at several junctures the subject of invasion of the Hawaiian Islands arose. As late as September 1941, a proposal was put forth to invade using two divisions of troops, approximately 30,000 men, supported by the carrier strike force and an invasion fleet of about 75-80 ships. Minoru Genda, chief planner for the attack, supported the idea of invasion, believing that occupation of the Hawaiian Islands by the Japanese would force the Americans to sue for peace. Japanese forces in Hawaii threatened the West Coast of the United States, as well as the Panama Canal after America lost most if not all of its Pacific Fleet. Genda went so far as to recommend invasion of Hawaii rather than the Philippines. Preliminary studies indicated it would take the Japanese roughly one month to secure the islands following the initial raids.
In the Japanese military hierarchy, the Imperial Japanese Army (IJA) held sway over their seagoing counterparts. The Army opposed the invasion of Hawaii, largely because it diverted resources from their desired push to the south and east. Japanese war plans of the 1920s and 1930s focused on the seizure of the Philippines, removing the American presence from the Southwest Pacific and providing the Japanese with airbases and naval installations which threatened Australia and New Zealand. The Japanese Navy never formally approached the IJA with plans for an invasion, but private discussions soon indicated the Army would not support the idea. Too many of its resources were already tied up in China or committed to the Philippine Campaign. Whether an invasion of Hawaii would have succeeded remains a source of discussion among theorists and alternative history buffs.
Numerous officials predicted the attack on Pearl Harbor
In October 1941, Lord Louis Mountbatten visited the United States Naval installation at Pearl Harbor. Having recently been assigned to command the British aircraft carrier Illustrious, then under repairs in Norfolk, Virginia, Mountbatten’s ostensible purpose for the visit was to brief American officers over British tactics against the Germans in the Mediterranean. Upon his return, Mountbatten visited Admiral Harry Stark, American Chief of Naval Operations. Mountbatten cited the general lack of preparedness present in Hawaii, in both the fleet and the defensive operations. He made several specific recommendations to Stark, based on the known Japanese penchant for surprise attacks and the British success at Taranto. Few, if any, were implemented. Mountbatten predicted a surprise attack at Pearl Harbor would bring the United States into the war, though he did not say when.
Among his recommendations was the deployment of torpedo nets to protect the battleships in port, which the Navy ignored. Senior Pacific Fleet staff argued the harbor itself offered protection against torpedo attack, being so shallow, and that deployment of the nets hampered other operations. Both the US Army and Navy in Hawaii remained in training status, rather than operational status, a small but significant bureaucratic distinction. Operational units had priority over training units for budget purposes. It also meant that live ammunition for the harbor defenses, and even aboard some ships, remained locked up. Aboard the American battleships, watertight doors remained open, and the ships presented little in the way of material readiness for combat, despite the fleet being under a war warning. Only the carriers were on an operational basis, but they weren’t in Pearl Harbor on December 7.
American security was tight in the days leading to the Pearl Harbor attack
On March 27, 1941, the Japanese liner Nitta Maru arrived in Honolulu carrying a new Japanese Consul-General, Nagao Kita, and his vice-consul, Tadashi Morimura. Both quickly became involved in espionage activities, tasked with obtaining information regarding the American fleet movements to and from Pearl Harbor. Morimura obtained rented quarters near Pearl City, in the hills overlooking the harbor, and studiously avoided the large Japanese-American community in the area. He preferred to take long walks alone in the hills overlooking the harbor, and around other military facilities in the region. He also cultivated a relationship with Bernard Kuehn, an agent working for the German Abwehr. Unknown to the American intelligence community at the time was Morimura was actually a former Japanese naval officer and intelligence agent of the name Takeo Yoshikawa.
Yoshikawa collected intelligence regarding ship movements, troop strengths, anchorages, schedules, and whatever else he could learn from observation and listening. These he transmitted via the Japanese Purple Code at the consulate to his handlers at the Japanese Foreign Ministry. Though the United States had by then broken the Purple Code, and intercepted his reports, no action was taken. The FBI and military intelligence considered most of the messages from the consulate to be commercial in nature, and thus of little interest to the military. Yoshikawa sent information routinely, much of which was used by Japanese commander Yamamoto in finalizing the preparations for the attack. He then destroyed all evidence of his activities. Following the attack, Yoshikawa and other Japanese diplomats were seized by the FBI, but by then no evidence of his espionage activities remained. He was returned to Japan in a diplomatic exchange, never charged as a spy.
Caught by surprise, Americans could do little to fight back
The attack on December 7th came in two waves. The first, detected on radar by the Army station at Opana, was misidentified as an expected flight of B-17s arriving from the mainland. A quick response by the army could have had several American fighters in the air when the Japanese arrived over the military installations, but it was not to be. Several ships outside the harbor also spotted the incoming Japanese; their reports were disregarded while awaiting confirmation. The American air defenses were caught completely by surprise. Nonetheless, during the course of the first wave, which began just before 8.00 AM local time, a handful of American fighters managed to get off the ground and engage the Japanese. After action reports credited six Army Air Force pilots with destroying Japanese aircraft during the attack, most in defense of the several airbases attacked.
Aboard the Navy’s ships, few senior officers were present when the attack began. There were some exceptions, and in some cases, the senior officers arrived aboard in the early stages of the attack. Sailors manned anti-aircraft guns and quickly began shooting at the enemy swarming over them from all directions at once. Aboard USS Nevada, preparations to get underway advanced rapidly. Nevada was the only American battleship to get underway during the attack. As it attempted to leave the harbor it came under such heavy attack, sustaining such severe damage its captain was forced to run the ship aground to prevent it from sinking in the channel, which would have closed the port until the ship could be moved. Oklahoma capsized with such speed hundreds of its crew were trapped below decks. It was during the first wave USS Arizona exploded, raining flaming debris across the oil-strewn harbor.
USS Arizona was responsible for almost half of all American fatalities
The explosion of USS Arizona, which destroyed the entire forward section of the ship, remains a subject of debate eighty years later. One theory is that the fatal bomb, which struck the ship at 8.06, detonated in an area where black powder, used to fire ceremonial salutes, was improperly stored. Another theory suggests the bomb penetrated the armored deck, detonating in the forward magazine. The massive explosion followed the bomb strike by just under 7 seconds, so either theory is possible, but it’s really quibbling over details. The forward magazines exploded, regardless of what the final trigger was, and the result was 1,177 men killed, most of them instantly. More than two-thirds of Arizona’s crew died in the explosion and its immediate aftermath, among them Captain Franklin Van Valkenburgh and Rear Admiral Isaac Kidd. About half of the deaths during the Pearl Harbor attack occurred aboard Arizona.
Arizona’s destruction triggered fires which spread to the oil covering much of the area around Battleship Row and contributed to the loss of at least one more American battleship. USS California, moored alone at the far end of the row, received two bomb hits, and at least two torpedo hits of its own. Its crew lost electrical power temporarily but were in the process of restoring it when burning oil drifted down on the stricken ship. California abandoned ship, but by late morning its crew came back aboard. Attempts to counterflood to control the list on the ship, as well as pumping out the ship, remained hampered by the lack of electrical power. California gradually settled to the harbor mud, its main deck partially awash. Like the other battleships lost that day, other than Oklahoma and Arizona, California was eventually raised, rebuilt, and returned to service.
Pearl Harbor was the major Japanese attack in the Pacific that December
Within a span of less than eight hours following the Japanese strike at Pearl Harbor, American, British, and Dutch possessions in the Pacific also came under attack. In all cases, they struck enemy airfields and, where relevant, Naval installations. American bases in the Philippines, Guam, and Wake Island were assaulted almost simultaneously. All received severe damage and casualties. British installations in Malaya and Singapore, the latter called by Churchill the bastion of the Empire, came under attack. Even before the American Congress heard FDR’s request for a declaration of war against Japan, the British Empire had declared war. Churchill himself directed a British task group, consisting of HMS Prince of Wales and HMS Repulse, to support the defense of Malaya. Both were sunk by Japanese air attack on December 10.
By that time there were already calls across the United States for an investigation into what happened at Pearl Harbor, as well as open accusations of Roosevelt having foreknowledge of the attack. One area of focus among those who believe FDR knew of the impending attack was the absence of the American aircraft carriers from Pearl Harbor. The theory suggests FDR had the Navy remove the carriers to protect them from harm, and ignores naval doctrine of the day. In December 1941, aircraft carriers were not considered capital ships by navies which adopted the Mahan Doctrine (including Great Britain, the United States, and Japan). Battleships and heavy cruisers comprised capital ships, carriers were considered part of the fleet’s scouting forces. The Pearl Harbor debacle led the world’s fleets to reconsider the value of aircraft carriers.
American carriers were absent to prevent them from being attacked
American carriers were absent to prevent they are being attacked, The United States had three aircraft carriers in the Pacific in December 1941. USS Saratoga was in a scheduled refit in Puget Sound. Lexington and Enterprise were both returning from missions during which they reinforced Marine aviation groups, the former at Midway, the latter at Wake Island. Had Enterprise been on schedule, the carrier would have entered port on December 6, after dispatching its air groups to the Naval Air Stations at Pearl Harbor. Heavy weather encountered during its return from Wake Island delayed its arrival by about 24 hours. During the attack, Enterprise was about 200 miles from Pearl Harbor, and planes from its air groups arrived over Hawaii as the attack was underway. Additional aircraft arrived following the Japanese raid and were subjected to friendly fire by the understandably jittery gun crews on the island.
The fact is, the battleships of the US Pacific Fleet were considered by the Navy at the time as the most valuable asset present at Pearl Harbor. Although the United States had other battleships which could be transferred to the Pacific, including Colorado, Idaho, New Mexico, New York, and Mississippi among others, it could ill afford the loss of the ships destroyed on December 7. It was from the Japanese the United States, and Great Britain, learned the value of aircraft carriers massed together as an offensive weapon at sea. With a couple of notable exceptions, the battleship was relegated to task force defense and shore bombardment following the attack on Pearl Harbor. The majority of the surface engagements which occurred in the Pacific during the war involved cruisers and destroyers. Fleet actions involved aircraft carriers, usually well out of sight of each other.
Pearl Harbor remains controversial eight decades on
Following the war, the attack on Pearl Harbor, an assault by a belligerent against a neutral nation, was designated a war crime. A total of 2,403 Americans were killed in the surprise attack, the first of over 100,000 who lost their lives during the Pacific War. During the Tokyo War Crimes Trials, Japanese Prime Minister Hideki Tojo, Navy Minister Shigetaro Shimada, Foreign Minister Shigenori Togo, and Osami Nagano, Chief of the Naval Staff, were charged with and convicted of war crimes involving the Pearl Harbor attack. Yamamoto, who planned the attack, and Nagumo, who commanded the task force which accomplished it, were both dead by then. Conspiracy theorists and revisionists believe FDR should have been charged as well, though the evidence he was aware of the pending attack and deliberately covered it up does not, for the most part, stand up to close examination.
By the late 1990s, the stirring World War II call to “Remember Pearl Harbor” had faded from memory. The attack is barely mentioned in American schools and history textbooks in the 21st century. The grandchildren of Americans who huddled by their radios on December 7, 1941, are largely unaware of the date’s significance. In Japan, schools teach it as just one event in the long war to protect Asia from European colonialization and exploitation, which began in 1931 and continued until the atomic bombing of Japan in 1945. USS Arizona remains where it sank, stripped of all salvageable parts, part of the Pearl Harbor National Memorial. Eighty years after its destruction the hull still seeps fuel oil, a few drops at a time which rise to the surface above, easily seen by those who visit the remains of the ship.
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