By autumn 1941 the Japanese Empire was committed to its Greater East Asia Co-Prosperity Sphere expansion programme. Japanese troops had occupied northern French Indochina in 1940 and southern Indochina in July 1941. The US response had been a progressive embargo on Japanese strategic imports — particularly oil, scrap iron, and aviation fuel — that the Japanese Empire depended on for its continued military operations in China.
By November 1941 the Japanese cabinet under Hideki Tojo had concluded that war with the United States was unavoidable. The strategic objective was to destroy the US Pacific Fleet in a pre-emptive strike, secure the Dutch East Indies oil resources, and fortify a perimeter that the United States would find too costly to break.
The Pearl Harbor strike plan was designed by Admiral Isoroku Yamamoto.
The strike force
Six Japanese aircraft carriers — Akagi, Kaga, Sōryū, Hiryū, Shōkaku, Zuikaku — under Vice-Admiral Chuichi Nagumo departed northern Hokkaido on 26 November 1941 by a northern Pacific route. They reached the launch point approximately 220 nautical miles north of Oahu on the morning of 7 December 1941 without being detected.
The first wave of 183 aircraft launched at 6:00 a.m. Hawaii time. The second wave of 170 aircraft launched approximately one hour later. Total Japanese aircraft committed: 353.
7:48 a.m. on 7 December 1941
The first Japanese aircraft crossed the Oahu coast at approximately 7:48 a.m. on Sunday 7 December 1941. The US Army radar station at Opana Point had detected the incoming formation 48 minutes earlier but had been told by the duty officer that it was probably the expected B-17 flight from California.
The bulk of the US Pacific Fleet was in port at Pearl Harbor. The battleships Arizona, Oklahoma, California, Nevada, Pennsylvania, Tennessee, Maryland, and West Virginia were moored along Battleship Row. The aircraft carriers — Enterprise, Lexington, Saratoga — were at sea on training and delivery missions and not in port.
The first Japanese bombs struck at approximately 7:55 a.m. The Arizona’s forward magazine exploded at approximately 8:06 a.m. from a penetrating armour-piercing bomb. The ship sank in nine minutes with 1,177 men aboard — nearly half the total American death toll.
The Oklahoma capsized at approximately 8:08 a.m. after multiple torpedo hits. Approximately 429 men died aboard.
The attack continued for approximately 110 minutes. The second wave completed by approximately 9:45 a.m. The Japanese strike force retired northward.
The casualties
The total American casualties were:
— Killed: 2,403 (military and civilian combined) — Wounded: 1,178 — Sunk or damaged: 8 battleships, 3 cruisers, 3 destroyers, 1 auxiliary ship — Aircraft destroyed: 188 on the ground (about 60 percent of the US Army Air Forces in Hawaii)
Japanese casualties were 29 aircraft and approximately 64 dead.
What did not happen
The Japanese strike produced two strategic failures that defined the subsequent Pacific war.
The US aircraft carriers had not been in port. The Pacific war turned out to be carrier warfare rather than battleship warfare; the Japanese had missed the decisive ship class.
The oil storage tanks at Pearl Harbor — approximately 4.5 million barrels of fuel oil that the US Pacific Fleet depended on — were untouched. The Japanese third-wave attack that would have destroyed the tanks was cancelled by Nagumo, who decided to withdraw rather than risk further engagement. The intact fuel permitted the US Pacific Fleet to operate from Pearl Harbor throughout 1942.
8 December
President Franklin D Roosevelt addressed a joint session of Congress on the morning of 8 December 1941. The speech included the phrase “a date which will live in infamy” and requested a declaration of war on Japan. Congress voted within the hour: 82-0 in the Senate, 388-1 in the House. The sole vote against was Jeannette Rankin, a Montana pacifist who had also voted against the 1917 US declaration of war.
Germany declared war on the United States on 11 December 1941. Italy followed the same day. The Second World War became a global war.
The Arizona
The wreck of the USS Arizona remains at the bottom of Pearl Harbor as a war grave. Approximately 900 of the 1,177 men killed aboard her are still entombed within the wreck. The Arizona Memorial — a white concrete structure spanning the wreck above the water line — was completed in 1962. Approximately 1.8 million visitors visit each year. The ship continues to leak approximately 9 litres of oil per day into the harbour, 84 years after the sinking.