Pearl Harbor Attack | Date, History, Map, Casualties, Timeline, & Facts

Warnings and responses

The U.S. Pacific Fleet had been stationed at Pearl Harbor since April 1940. In addition to nearly 100 naval vessels, including 8 battleships, there were substantial military and air forces. As the tension mounted, Adm. Husband E. Kimmel and Lieut. Gen. Walter C. Short, who shared command at Pearl Harbor, were warned of the possibility of war, specifically on October 16 and again on November 24 and 27. The notice of November 27, to Kimmel, began, “This dispatch is to be considered a war warning,” went on to say that “negotiations have ceased,” and directed the admiral to “execute an appropriate defensive deployment.” Kimmel also was ordered to “undertake such reconnaissance and other measures as you deem necessary.” The communication of the same day to Short declared that “hostile action is possible at any moment” and, like its naval counterpart, urged “measures of reconnaissance.”

Britannica Quiz Pop Quiz: 17 Things to Know About World War II

In response to these warnings, the measures taken by the army and navy commanders were, as the event proved, far from adequate. Short ordered an alert against sabotage and concentrated most of his fighter planes at the base on Wheeler Field in an effort to prevent damage to them. He also gave orders to operate five of the mobile radar sets that had been set up in the island from 4:00 am to 7:00 am, considered to be the most dangerous period. (Radar training, however, was in a far-from-advanced stage.)

Kimmel, despite the fact that his intelligence had not been able to locate substantial elements in the Japanese fleet—especially the first-line ships in carrier divisions 1 and 2—did not expand his reconnaissance activities to the northwest, the logical point for an attack. He moored the entire fleet (save that part which was at sea) in the harbor and permitted a part of his personnel to go on shore leave. Neither of these officers suspected that the base at Pearl Harbor would itself be subjected to attack. Nor, for that matter, is there any indication that their superiors in Washington were in any way conscious of the approaching danger. In the 10 days between the war warning of November 27 and the Japanese attack itself, no additional action was taken by Washington.

Explore Britannica Premium!

The trusted destination for professionals, college students, and lifelong learners.

SUBSCRIBE

Early on Sunday morning, December 7, Washington learned that the Japanese ambassadors had been instructed to ask for an interview with the secretary of state at 1:00 pm (7:30 am Pearl Harbor time). This was a clear indication that war was at hand. The message took some time to decode, and it was not in the hands of the chief of naval operations until about 10:30. It was delivered to the War Department between 9:00 and 10:00 am. Gen. George C. Marshall, the U.S. Army chief of staff, was out horseback riding and did not see the dispatch until he arrived at his office about 11:15 am. The chief of naval operations, Adm. Harold Stark, even then did not think that the communication called for any additional instructions to Kimmel. However, Marshall did decide to send a new warning and gave orders to the military command to communicate with the navy. He did not telephone, fearing that his words might be intercepted, and instead sent his dispatch by telegram. There was a mix-up in communication, however, and the warning did not reach Hawaii until after the attack had begun. It is important to note that it had not been filed until noon, only an hour before the Japanese planes moved in on the base.

Quick Facts Date: December 7, 1941 (Show more) Location: Hawaii Oahu United States (Show more) Participants: Japan United States (Show more) Context: Operation Barbarossa Pacific War Second Sino-Japanese War World War II (Show more) Key People: Nagano Osami Tōjō Hideki Yamamoto Isoroku Husband Edward Kimmel Walter Campbell Short (Show more) See all related content

At Pearl Harbor itself, there were incidents that, properly interpreted, might have given a brief warning. Four hours before the decisive moment, a Japanese submarine was sighted by the minesweeper USS Condor. About two and a half hours later, the commander of the destroyer USS Ward sent a message saying that he “had attacked, fired upon, and dropped depth charges upon submarine operating in defensive sea area” near Pearl Harbor. While Kimmel waited for confirmation of this report, the Japanese opened hostilities. In these same morning hours, U.S. Army Pvt. George Elliott, practicing on the radar set after its normal closing time, noticed a large flight of planes on the screen. When he telephoned his lieutenant, he was told to disregard the observation, as a flight of B-17 bombers from the United States was expected at that time. Once again an opportunity was missed.