inlet of the island of Oahu, Hawaii, about 10 km (about 6 mi) west of Honolulu. It is the site of one of the principal naval bases of the U.S.

The U.S. government first obtained exclusive use of the inlet and the right to maintain a repair and coaling station for ships here in 1887. The harbor was surveyed then and later, but improvements were not begun until after the U.S. annexed the Hawaiian Islands in 1898. In 1911 the work of dredging a wide channel from the sea, across the sandbar and coral reef at the mouth of the harbor, was completed. The channel is about 11 m (about 35 ft) deep, and the harbor has a maximum depth of 18 m (60 ft), making the harbor available to the largest naval vessels.

Early in the morning of Dec. 7, 1941, Japanese submarines and carrier-based planes attacked the U.S. Pacific fleet at Pearl Harbor. Nearby military and naval airfields were also attacked by the Japanese planes. Eight American battleships and 10 other naval vessels were sunk or badly damaged, almost 200 American aircraft were destroyed, and approximately 3000 naval and military personnel were killed or wounded. The attack marked the entrance of Japan into World War II on the side of Germany and Italy and of the U.S. on the Allied side.

Soon after the attack U.S. President Franklin D. Roosevelt appointed a commission of inquiry to determine whether negligence had contributed to the success of the Japanese raid on Pearl Harbor. The commission’s report found the naval and army commanders of the Hawaiian area, Rear Adm. Husband E. Kimmel (1882–1968) and Maj. Gen. Walter C. Short (1880–1949), guilty of “derelictions of duty” and “errors of judgment”; the two men were subsequently retired. Other later inquiries, however, differed in their conclusions. The U.S. Congress, in an effort to dispose of the controversy, decided on a full, public investigation after the war.

The bipartisan congressional committee opened its investigation on Nov. 15, 1945. Testimony from many people reviewed all known information about the attack on Pearl Harbor. The committee reported on July 20, 1946. It placed the primary blame on Gen. Short and Adm. Kimmel, who, however, were declared guilty only of errors of judgment, and not of derelictions of duty. The committee recommended the unification of the U.S. armed forces, which occurred the following year.