On December 7, 1941, Japanese forces attacked the Hawaiian naval base at Pearl Harbor. The attack on American naval vessels and installations was intended to neutralize the Pacific Fleet and allow Japan to consolidate its control over Southeast Asia without the interference of the United States. The attack caught the United States by surprise; though relations between the two nations had been tense for more than a decade, exacerbated by the Japanese expansion into French Indochina earlier that year, diplomatic talks had continued up to the attack on Pearl Harbor.

On December 7, 1941, Japanese forces attacked the Hawaiian naval base at Pearl Harbor. The attack on American naval vessels and installations was intended to neutralize the Pacific Fleet and allow Japan to consolidate its control over Southeast Asia without the interference of the United States. The attack caught the United States by surprise; though relations between the two nations had been tense for more than a decade, exacerbated by the Japanese expansion into French Indochina earlier that year, diplomatic talks had continued up to the attack on Pearl Harbor.

The attack launched just before 8 a.m. By the time the Japanese forces withdrew nearly two hours later, they had sunk or damaged twenty-one ships of the US Pacific Fleet and had inflicted significant aircraft losses, resulting in more than twenty-four hundred casualties. The situation at Pearl Harbor was chaotic, and communication systems were damaged. This memorandum is the first written damage assessments given to President Franklin D. Roosevelt, though he had received an earlier phone call informing him that Pearl Harbor was under attack. This document is an important record of the situation in Pearl Harbor as it was understood by the US Navy immediately after the Japanese attackers had withdrawn.

Relations between Japan and the United States began to deteriorate in the 1930s following Japan’s invasion of Chinese Manchuria, in clear violation of the League of Nations. The League failed to stop the invasion, and Japan withdrew its membership. Rising Japanese militarism combined with virulent nationalism convinced the nation’s rulers of their right to conquer and control all of Asia, including territory then controlled by the British, the Dutch, the Americans, and the Chinese.

In 1937, Japan invaded China on a massive scale, capturing major cities and slaughtering soldiers and civilians alike. The invasion of China dragged on for years, and the Japanese government’s need for raw materials such as oil and rubber to carry out its military agenda grew critical. In 1940, Japan signed the Tripartite Pact, solidifying its alliance with Germany and Italy as the Axis powers. Japan next looked toward colonial territory in Southeast Asia to supply it with materials and forward its goal of control over the continent.

The United States, while deeply concerned with Japan’s growing aggression, wished to avoid war with the Axis powers at almost any cost. Opinion in the United States still supported an official policy of neutrality while providing material support for the Allies, including China. Fearing Japanese expansion, the United States first limited and then eliminated shipments of military supplies and oil to Japan, an act seen by the Japanese as aggressive.

In 1941, Roosevelt moved the US Pacific Fleet from San Diego, California, to Pearl Harbor and to reinforced military bases in the Philippines, hoping to discourage further expansion. The United States cut off all oil shipments in July 1941 after Japan invaded French Indochina, and took advantage of France’s collapse and takeover by Germany. In August, Roosevelt warned Japan not to attack its neighbors and entered into diplomatic negotiations to forestall further territorial expansion. Japan, dependent on foreign oil and raw materials, faced a choice between war with the United States and a withdrawal from land that the government felt it should control by right. Japanese military leaders determined that a preemptive strike on the US Pacific Fleet, supported by simultaneous attacks on the Philippines, Hong Kong, Singapore, and Malaya, would cripple the United States and allow Japan to consolidate its control over Asia.

On December 7, 1941, just before 8 a.m., the naval base at Pearl Harbor was attacked by 353 Japanese fighter planes, launched by six aircraft carriers and supported by submarines. The attack damaged all of the US Navy battleships present. Airfields were bombed and strafed simultaneously to prevent counterattack. One hundred and eighty-eight planes were destroyed and another 159 were damaged. The entire attack lasted just about two hours, during which time the United States lost more than twenty-four hundred military personnel, including sixty-eight civilians.

President Roosevelt was at lunch when Secretary of the Navy Frank Knox called to report the attack on Pearl Harbor. By 3:50 p.m., Knox had received his first damage reports and passed them on to the president. Although the attack on Pearl Harbor achieved its aim of crippling the Pacific Fleet, it also served to galvanize the nation behind Roosevelt and his determination to go to war with the Axis powers. War with Japan was declared the following day.

The US Navy dates its formation to October 1775, when the Continental Congress established the Continental Navy, several months after the start of the Revolutionary War. Following the end of the war, the navy’s remaining ships were sold and its personnel dismissed; this state of disarmament lasted until 1794, when the US Congress, empowered by the recently ratified Constitution, passed the Naval Act of 1794.

At the time of the attack on Pearl Harbor, the secretary of the navy was William Franklin “Frank” Knox, who had previously been a Rough Rider under Theodore Roosevelt in the Spanish-American War, a newspaper editor and publisher, and the 1936 Republican candidate for vice president. Although Knox and his running mate were soundly defeated by incumbent president Franklin D. Roosevelt, following the election, Roosevelt appointed Knox to the secretary position, as he relied on bipartisan support for his foreign policy in the run-up to Pearl Harbor. On the day of the attack, Knox called the president at 1:40 p.m. eastern standard time to inform him of what had transpired. Roosevelt received the memorandum, prepared by the US Department of the Navy, just over two hours later.

Memorandum for the President

The Japs attacked Honolulu time about eight o’clock this morning. The first warning was from a submarine that was outside the harbor which was attacked by a destroyer with depth bombs. Result unknown. Another submarine was sunk by aircraft. They attacked with aircraft, with bombs and torpedoes. At least two aircraft were known to have a swastika sign on them. The attacks were in two divisions; first on the airfields and then on the navy yard. Severe damage. The Oklahoma has capsized in Pearl Harbor. The Tennessee is on fire with a bad list., and the navy yard is attempting to dry dock her.

No. 1 drydock was hit by bombs. The Pennsylvania was in dock and apparently undamaged. There were two destroyers hit in drydock, one of them blew up. There was one destroyer in a floating drydock which is on fire and the deck is being flooded. Two torpedoes it the sea wall between the Helena, which is 10,000 tons–6 in. cruiser, and the Oglala. The Oglala is heavily listed and can probably not be saved. She is on fire and is an old mine layer. The power house at Pearl Harbor was hit but is still operating. The Honolulu power house was presumably hit because there is no power on it. The air fields at Ford Island, Hickam, Wheeler and Kanoehe [Kaneohe] were attacked.

Hangars on fire and Hickam field fire is burning badly. The PBYs outside of hangars are burning. Probably heavy personnel casualties but no figures. So far as Block knows Honolulu was not hit. He does not know how many aircraft were brought down but he knows personally of two. They have both been so busy he has not contacted Kimmel. There are two task forces at sea, each one of them with a carrier. He knows nothing further on that except that they are at sea. This came over the telephone and we are getting nothing out here whatever. Mr. Vincent called but I have given out nothing, pending further word from you. The Japanese have no details of the damage that they have wrought.

depth bombs: an explosive device that is used against submarines and other underwater targets and is usually set to detonate at a predetermined depth

drydock: a structure able to contain a ship and to be drained or lifted so that the ship is free of water with all parts of the hull accessible for repair and maintenance

Japs: a term used to refer to a Japanese person; derogatory slang

list: a careening, or leaning to one side, as of a ship

PBY: a type of amphibious bomber aircraft, also called a Catalina

This memo is intended to convey urgency and was presumably written in haste. As such, it has a more conversational tone than is generally found in military documents, stating that “the Japs attacked… about 8 o’clock this morning.” Though responsibility for the attack clearly lies with Japan, the report also mentions eyewitness accounts of “at least two aircraft” with “a swastika sign on them”—a statement that would later prove to be incorrect.

The first warnings of the attack were from submarine activity, and one Japanese submarine was sunk before dawn. The memo lays out the most important details first: the two waves of bombings that hit the harbor, airfields, and navy yard; the burning of the battleship USS Tennessee; and the destruction of USS Oklahoma, which is described as “capsized.” Due to the confusion of the first hours following the attack, the damage to USS Arizona, which was set ablaze by a bomb, is not noted. The fire and explosion led to the greatest death toll aboard any ship on that day. The Arizona lost 1,177 crew members, about half of those killed that day.

The report goes on to list damage to battleships and other craft, airfields, and electrical stations. The report states incorrectly that USS Pennsylvania, a battleship, was undamaged; in fact, the Pennsylvania was hit repeatedly, resulting in fifteen dead and thirty-eight wounded. The memo also reported that to the best of the Navy’s knowledge, Honolulu had not been hit. This was also not accurate, as the city sustained significant damage from projectiles, though some of these were a result of friendly fire.

In the immediate aftermath of the attack on Pearl Harbor, the extent of the damage was difficult to ascertain with any accuracy, as this report attests. The information it contains is inaccurate and incomplete due to the breakdown of communications on the ground. The memo reports that there were “probably heavy personnel casualties” but that “no figures” are available. Similarly, the Navy “does not know how many aircraft were brought down” and “knows nothing further” about two task forces that are unaccounted for, other than that they are at sea and each one has a battleship. The frustration of the memo’s author is evident in the statement, “We are getting nothing out here whatever.”

This memorandum is the first detailed report given to President Roosevelt after the attack on Pearl Harbor. Its incompleteness and inaccuracy was the result of poor communications, unreliable witnesses, and chaos on the scene. The erroneous report of aircraft bearing swastika symbols was repeated in several newspaper articles in the following days, further inflaming the American public against the Axis powers. This is an excellent example of how complex and confusing the attack was for those involved, as they tried to deal with the immediate danger they were in while also relaying information to those further up the chain of command. Still, the report contained the crucial information that Roosevelt needed to begin military action against Japan. The attack had been unexpected, unprovoked, and deadly.

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• “History of America: Pearl Harbor.” History.co.uk. AETN UK, n.d. Web. 3 Nov. 2014.
• Lord, Walter.Day of Infamy. 1957. New York: Holt, 2001. Print.
• “Overview of the Pearl Harbor Attack, 7 December 1941.” Naval History and Heritage Command. US Navy, n.d. Web. 3 Nov. 2014.