Operation K, was a Japanese naval operation in World War II, intended as a reconnaissance of Pearl Harbor and disruption of repair and salvage operations following the surprise attack on December 7, 1941. It culminated on March 4, 1942, with an unsuccessful attack carried out by two Kawanishi H8K “Emily” flying boats. This was the longest distance ever undertaken by a two-plane bombing mission, and the longest bombing sortie ever planned without fighter escort

The SECOND Raid on Pearl Harbor – Operation K

Everyone knows about the First Pearl Harbor Attack by the Japanese Imperial Navy. But few are aware of the second Raid that the Japanese launched on Pearl Harbor. This raid was codenamed Operation K. It was a Japanese naval operation in WWII intended as a reconnaissance mission of the US Naval base at Pearl Harbor.

During the Pearl Harbor attack, the Japanese had missed out on destroying the Oil Storage facilities near Pearl Harbor Naval Air Station and the Naval Yard. So, they aimed to bomb these facilities in Operation K. Also, the Japanese aimed to disrupt the repair and salvage operations that were going on in full swing. This was, perhaps, the longest bombing sortie by two planes without fighter escort in WWII.

Operation K culminated on March 4, 1942. Two, nicknamed “Emily,” carried out an unsuccessful attack on Pearl Harbor. These flying boats were huge with a gross takeoff weight of 71,650 lb and a wingspan of 124 ft. Four 1,850 hp engines powered this flying boat. Its top speed was 296 mph, and it had a crew of 10. Named “the Flying Porcupine” by Allied pilots, this flying boat was defended by 10 machine guns and an equal number of 20mm cannons. The H8K flying boat was capable of undertaking long missions that lasted up to 24 hours. Each flying boat could carry eight 550 lb bombs.

Initial plans of the Japanese Navy’s high command called for the use of 5 H8K aircraft. They were to fly to French Frigate Shoals, the biggest atoll in the Northwestern tip of the Hawaiian Islands. Here, they’d be refueled by submarines before heading to Pearl Harbor. More raids would be undertaken if the first raid was successful.

On mission day, only two of the planned 5 flying giants were available. The first H8K aircraft was flown by Pilot Lieutenant Hisao Hashizume, the commander of the mission. Ensign Shosuke Sasao was flying the second H8K. The mission started at Wojte Atoll (Marshall Islands). Each aircraft was loaded with four 550 lb bombs. From Wojte, the flying boats flew 1,900 mi to French Frigate Shoals. After refueling here, the planes set off for Pearl Harbor that was 560 mi away.

The Ten-Ten dock was so named because of it length—1,010 ft. The US Navy’s salvage and repair efforts were in progress at this dock. The time of the bombing was to be sometime after midnight. However, the Japanese plan of bombing the Ten-Ten Dock was hindered due to the prevalent unfavorable weather conditions at Pearl Harbor. Inclement weather also resulted in a several errors. The Japanese submarine I-23 that was supposed to direct the flying boats south of Oahu was lost after February 14.

Ships docked at Ten-Ten Dock

Hawaii’s WARD—Women’s Air Raid Defense—picked up the Japanese planes on their Radar. They had been working for 12 weeks since the Pearl Harbor Attack and were on high alert. The response to the women’s alert was instantaneous. Searchlights were turned on, fighter planes were scrambled, and the anti-aircraft guns were manned. Since it was a moonless, rainy night, the fighter planes were not successful in downing the flying boats (Altitude: 15,000 ft) even with help from the WARD Radar operators.

Pearl Harbor SCR-270 Radar Station

In the absence of position support from their submarine I-23, the Japanese Pilots used the lighthouse at Kaena Point for a position fix. Mission Commander Hashizume attacked from the north. Poor quality radio communication resulted in the second pilot, Sasao, turning to skirt the opposite (north) coast of Oahu. In the inclement weather, Hashizume was able to see just some patches of the island. He dropped his 4 bombs on the Tantalus Peak sometime around 2 am local time. The bombs landed close to Roosevelt High School, but the damage was minimal.

Sasao dropped the 4 bombs he carried into the ocean somewhere close to the sea approach to Pearl Harbor and returned to Wotje Atoll. Hashizume, whose aircraft had sustained hull damage at French Frigate Shoals, proceeded to his home base at Jaluit Atoll.


Operation K was a colossal failure. The mission was jinxed right from the beginning. Only two porcupines flew instead of the planned five. Also, the absence of an element of surprise and poor weather conditions forced the Japanese planes to drop their bombs blind when they could not sight their targets. The flying giants returned without success.

Source: http://www.warhistoryonline.com