December, 1941: Battle of Pearl Harbor Summary

  • Last updated on November 11, 2022

The surprise attack by Japanese naval air forces upon the huge United States naval base at Pearl Harbor, Hawaii, has become synonymous with duplicity and cunning. Nevertheless, the circumstances of the attack engendered bitter controversy over the reasons for the failure of U.S. leaders to anticipate and to defend themselves against this devastating blow.

The surprise attack by Japanese naval air forces upon the huge United States naval base at Pearl Harbor, Hawaii, has become synonymous with duplicity and cunning. Nevertheless, the circumstances of the attack engendered bitter controversy over the reasons for the failure of U.S. leaders to anticipate and to defend themselves against this devastating blow.


In retrospect, Pearl Harbor can be explained without recourse to a “devil theory of war”–that Japan, unprovoked by the United States, deliberately and wantonly struck the Navy’s Pacific command center. Given the Japanese military and political situation and the dictates of Japanese strategic thinking, the attack was the logical result of a series of confrontations between Japan and the United States. Although U.S. interest was focused primarily on Europe between 1939 and 1941, events in the Far East aroused increasing concern in Washington, D.C., as Japan carried forth its ambitious creation of a Japanese-dominated Greater East Asia Co-Prosperity Sphere, which championed “Asia for Asians.” Much of China had fallen under Japanese control by 1939. Japan officially became an Axis Power in September, 1940, with the signing of the Tripartite Pact–a “defensive” alliance among Germany, Italy, and Japan. By the summer of 1941, Japan had gained concessions in Indochina and was threatening to engulf Thailand, the Soviet Union’s Siberian provinces, the British bastion of Singapore, Burma, the Dutch East Indies, and the Philippines.

The United States opposed this Japanese expansion primarily with economic sanctions. Throughout the 1930’s, as Japan seized Manchuria and moved against China, the United States proved unable or unwilling to oppose Japan by force. Although sympathetic toward China, President Franklin D. Roosevelt was more concerned about Germany than about Japan. Supported by Navy spokesmen who feared that a two-ocean war would lead the United States to disaster, Roosevelt adopted a policy of caution toward Japanese expansion in the hope that liberal Japanese leaders would wrest power from the more militant imperialists and reverse Japan’s course. Despite British and Dutch pressure, the United States was slow to accept the necessity of economic sanctions until August, 1940, when Roosevelt imposed an embargo on aviation gasoline. Restrictions on the export of scrap iron and steel followed in September, 1940, and Japanese assets in the United States were frozen in July, 1941.

Japanese leaders, almost all of whom supported the program of expansion and differed only on how it should be accomplished, came to believe that Japan was being encircled by the Western powers. If Japanese demands were not achieved by diplomacy, military force would become necessary. Economic sanctions by the United States, Great Britain, and the Netherlands–especially the embargo–meant that Japan had to choose between peace and war within a year, before its oil reserves were exhausted. In July, 1941, an advance into Southeast Asia for oil and other resources was approved by the Japanese Imperial Council, even if it meant war with the United States. On September 6, an Imperial Conference set what amounted to a time limit on diplomatic efforts for the settlement of negotiations with the United States. Negotiations continued, with neither side offering concessions. Roosevelt and Secretary of State Cordell Hull were pessimistic but believed that discussions should continue, in order that the United States might gain time for defense preparations.

Meanwhile, Army and Navy intelligence at Pearl Harbor and in Washington, D.C., learned that Japan might be planning to mount a surprise attack, but the evidence was fragmentary. U.S. military planners knew from intercepted messages that things would happen automatically if the U.S. rejected a final Japanese proposal, but most indications pointed to an attack somewhere in Southeast Asia. Ambassador Kichisaburo Nomura of Japan presented to Hull what was to be the final Japanese proposal for peace on November 10. Hull declared it unacceptable and on November 26 made a counteroffer, which he knew from intercepted Japanese messages would be rejected. Diplomacy proved futile. On Sunday, December 7, while Japanese planes were making their bomb runs over Pearl Harbor, a Japanese diplomatic note was handed to the secretary of state; it implied disruption of relations, but it was not a declaration of war.

Japanese Preparations

Japan’s preparations for the attack on Pearl Harbor had begun with tactical planning in the early months of 1941. Japanese strategists recognized that an advance into Southeast Asia would likely generate a U.S. military response. Destruction of the United States Pacific Fleet based in Hawaii was essential if Japan’s move into the region was to succeed. A daring plan by Admiral Isoroku Yamamoto to destroy or cripple the fleet at anchor in Pearl Harbor was at first considered impractical, if not suicidal, but the proposal was later accepted when table-top games proved it workable and Yamamoto exerted his powerful influence in favor of it. Pilots began training in September, and all objections were overcome. To cope with the shallow waters of Pearl Harbor, wooden-finned torpedoes were devised, together with a new method of delivering them on target; elaborate precautions were undertaken to preserve secrecy; and abundant intelligence was gathered concerning the movements of the U.S. Pacific Fleet.

Under the command of Vice Admiral Chuichi Nagumo, a special task force of thirty-one vessels, including six aircraft carriers that carried 432 airplanes–fighters, dive-bombers, high-level attack bombers, and torpedo planes–left Japanese ports in early November. On November 22, this force gathered in the Southern Kuriles. Four days later, it headed out to sea for a run of 3,500 miles to a rendezvous point 275 miles north of Pearl Harbor. The strike force was not to attack until final clearance for action was issued from the Japanese high command. On December 2, the signal “Climb Mount Niitaka” was received by Nagumo and the date of attack confirmed. Early on December 7, the strike force reached position, so that the first Japanese planes were flying over Pearl Harbor by 7:55 a.m., local time.

The Attack

The weather was ideal for an attack, and Pearl Harbor was caught totally unprepared. The blow was deliberately planned for Sunday morning, when the ships of the Pacific Fleet were moored in perfect alignment and their crews were ashore, having breakfast, or relaxing on board ship. There was no advance warning in Hawaii. An operator at a temporary U.S. radar post observed the oncoming Japanese squadrons at 7:02 a.m.; he reported the blips shown on the radar screen, but the watch officer did not pass on the information, thinking they were a group of U.S. bombers expected to arrive that morning from the West Coast.

Japanese sailors give an enthusiastic sendoff to planes taking off from an aircraft carrier before the attack on Pearl Harbor. (National Archives)

The Japanese planes swooped to the attack. Fighters and dive-bombers strafed and bombed the neat rows of aircraft at Wheeler Field and the Naval Air Station. Torpedo planes and dive-bombers also attacked Battleship Row in the devastating first phase, which lasted thirty minutes. After a fifteen-minute lull, the Japanese launched high-level bombing attacks on the harbor, airfields, and shore installations, followed by more attacks by dive-bombers, which pressed through mounting antiaircraft fire. The last planes withdrew at 9:45 a.m., less than two hours after the attack had begun.

They left behind a scene of destruction and carnage without parallel in U.S. history. Casualties were 2,403 dead and 1,178 wounded. Three battleships–the West Virginia, Arizona, and California–were sunk; the Oklahoma lay capsized; and the Tennessee, Nevada, Maryland, and Pennsylvania suffered varying degrees of damage. Several smaller warships were sunk, and others were seriously crippled. Almost all combat aircraft on the islands were damaged or destroyed. Twenty-nine Japanese airplanes were lost, along with one full-sized submarine and five midget submarines.

The destroyer USS Shaw explodes after its forward magazines are hit by bombs. Although the ship sustained heavy fire damage and lost its entire bow, it remained afloat the next day. (National Archives)


The U.S. forces in Hawaii fought courageously and recovered quickly from their initial shock. However, they were tragically unprepared to repel the skillful blows rained down by the Japanese strike force. The Japanese were successful far beyond the expectations of their high command; the United States Pacific Fleet lay grievously wounded and would not, Japan believed, be able to undertake offensive operations for months. The attack failed, however, in two particulars. First, the Japanese missed their prime targets: the aircraft carriers Lexington and Enterprise (both of which were at sea), and Saratoga (which was in dry dock on the West Coast). Second, the Japanese failed to destroy the huge oil storage facilities, without which the Pacific Fleet would have been forced to retire to the West Coast. While historical debate continues regarding the necessity of the attack for Japan and the lack of U.S. preparedness, the Pearl Harbor attack unified the U.S. people and eliminated whatever isolationist sentiment still existed in 1941. Within a few days, the United States was at war with Japan, and, because of the Tripartite Pact, with Germany as well.

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