For the Soviet series of high altitude nuclear tests, see The K Project

The K Project

The K Project, or also Operation K, was a series of five high altitude nuclear explosions, nuclear tests performed by the Soviet Union during the years 1961 and 1962. Their purpose was to test the performance of anti-ballistic missiles of the ABM System A and their resistance against nuclear blasts...

.

was a Japanese naval operation in World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

, intended as a reconnaissance

Reconnaissance

Reconnaissance is the military term for exploring beyond the area occupied by friendly forces to gain information about enemy forces or features of the environment....

 of Pearl Harbor

Pearl Harbor

Pearl Harbor, known to Hawaiians as Puuloa, is a lagoon harbor on the island of Oahu, Hawaii, west of Honolulu. Much of the harbor and surrounding lands is a United States Navy deep-water naval base. It is also the headquarters of the U.S. Pacific Fleet...

 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

Kawanishi H8K

|-See also:-References:NotesBibliography* Bridgeman, Leonard. "The Kawanishi H8K2 “Emily”" Jane’s Fighting Aircraft of World War II. London: Studio, 1946. ISBN 1-85170-493-0....

 "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.

Planning

The planning for Operation K began in the weeks after the attack on Pearl Harbor, when the Imperial Japanese Navy high command considered how to take advantage of the capabilities of the long-range H8K flying boats. Plans to bomb California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

 and Texas

Texas

Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...

 were being discussed, when the need for updated information regarding the repairs to US Navy facilities at Pearl Harbor took precedence. An assessment of the repairs to the docks, yards and airfields of O'ahu would help the IJN staff to determine American ability to project power for months to come.

Initial plans called for the use of five H8K aircraft. They would fly to Kānemilohai (also known as the French Frigate Shoals

French Frigate Shoals

The French Frigate Shoals is the largest atoll in the Northwestern Hawaiian Islands. Its name commemorates French explorer Jean-François de La Pérouse, who nearly lost two frigates when attempting to navigate the shoals...

), the largest atoll

Atoll

An atoll is a coral island that encircles a lagoon partially or completely.- Usage :The word atoll comes from the Dhivehi word atholhu OED...

 in the Northwestern Hawaiian Islands

Northwestern Hawaiian Islands

The Northwestern Hawaiian Islands or the Leeward Islands are the small islands and atolls in the Hawaiian island chain located northwest of the islands of Kauai and Niihau. They are administered by the U.S. state of Hawaii except Midway Atoll, which has temporary residential facilities and is...

, to be refueled by submarines prior to taking off for O'ahu. If the first raid was successful, additional raids would be made.

In a repeat of events just prior to the December 7 attack, American codebreakers warned that the Japanese were preparing for reconnaissance and disruption raids, refueling at Kānemilohai, and again were largely ignored by their superiors.

Execution

When time came for the raid, only two of the big flying boats were available. Pilot Lieutenant Hisao Hashizume was in command of the mission, and Ensign Shosuke Sasao flew the second plane. They were sent to Wotje Atoll

Wotje Atoll

Wotje Atoll is a coral atoll of 75 islands in the Pacific Ocean, and forms a legislative district of the Ratak Chain of the Marshall Islands. Wotje's land area of , is one the largest in the Marshall Islands, and encloses a lagoon of . The atoll is oriented east and west and is at its longest...

 in the Marshall Islands

Marshall Islands

The Republic of the Marshall Islands , , is a Micronesian nation of atolls and islands in the middle of the Pacific Ocean, just west of the International Date Line and just north of the Equator. As of July 2011 the population was 67,182...

, where each plane was loaded with four 550-lb bombs. From there, they flew 1900 miles (3,057.7 km) to French Frigate Shoals to refuel, then set off for O'ahu, 560 miles (901.2 km) distant. In addition to their reconnaissance mission, they were to bomb the "Ten-Ten" dock (named for its length, 1,010 feet) at the Pearl Harbor naval base to disrupt salvage and repair efforts. However, a comedy of errors ensued on both sides.

The Japanese submarine I-23

Japanese Type-B submarine

The was a class of submarine in the Imperial Japanese Navy which served during World War II. The Type-B submarines were similar to the Type-A apart from not having the headquarters installation.-Class variants:...

was supposed to station itself just south of Oahu as a "lifeguard" and weather spotter for the flying boats, but was lost sometime after February 14.

American radar stations on Kaua'i (and later O'ahu) picked up and tracked the two planes as they approached the main Hawaiian Islands, prompting a search by P-40 Warhawk fighters. PBY Catalina

PBY Catalina

The Consolidated PBY Catalina was an American flying boat of the 1930s and 1940s produced by Consolidated Aircraft. It was one of the most widely used multi-role aircraft of World War II. PBYs served with every branch of the United States Armed Forces and in the air forces and navies of many other...

 flying boats were also sent to seek Japanese aircraft carriers, which were assumed to have launched the two invaders. However, heavy clouds (and possibly an overcast below the H8Ks) prevented the defenders from spotting the Japanese planes, which were flying at an altitude of 15000 feet (4,572 m).

Those same clouds also confused the IJN pilots. Using the Ka'ena Point lighthouse for a position fix, Hashizume decided to attack from the north. Sasao, however, did not hear Hashizume's order and instead turned to skirt the southern coast of Oahu.

Hashizume, having lost sight of his wingman, and only able to see small patches of the island, dropped his four bombs on the slopes of Tantalus Peak

Tantalus (Oahu)

Tantalus is an extinct cinder cone in the southern Koolau Range on the Hawaiian Island of Oahu. It also has a summit crater, Tantalus Crater. The cinder cone formed after the demise of Koolau Volcano, during a time of rejuvenated stage volcanism in southeastern Oahu that also formed Punchbowl...

, an extinct volcano cinder cone just north of Honolulu sometime between 2-2:15am HST. He was unable to see Pearl Harbor, the only lit facility on Oahu due to blackout

Blackout (wartime)

A blackout during war, or apprehended war, is the practice of collectively minimizing outdoor light, including upwardly directed light. This was done in the 20th century to prevent crews of enemy aircraft from being able to navigate to their targets simply by sight, for example during the London...

 conditions intended to hinder air raids. Hashizume's bombs landed about 1000 feet (304.8 m) from Roosevelt High School

President Theodore Roosevelt High School

President Theodore Roosevelt High School is a public, co-educational college preparatory high school of the Hawaii State Department of Education and serves grades nine through twelve...

, creating craters 6–10 feet (1.8-3 m) deep and 20–30 feet (6.1-9.1 m) across. Damage was limited to shattered windows. Sasao is assumed by historians and officials to have eventually dropped his bombs into the ocean, either off the coast of Wai'anae or near the sea approach to Pearl Harbor. The two flying boats then flew southeast and proceeded to Jaluit Atoll

Jaluit Atoll

Jaluit Atoll is a large coral atoll of 91 islands in the Pacific Ocean, and forms a legislative district of the Ralik Chain of the Marshall Islands. Its total land area is only , but it encloses a lagoon with an area of . Most of the land area is on largest islet of Jaluit . Jaluit is located...

, also in the Marshall Islands.

Aftermath

No casualties were reported. The raid did however raise new fears of a potential Japanese invasion of Hawaii.

Japanese media reported an unsubstantiated Los Angeles radio report of "considerable damage to Pearl Harbor" with 30 dead sailors and civilians, with 70 wounded. Both the U.S. Army and U.S. Navy blamed each other for the explosions, accusing each other of jettisoning munitions into Tantalus.

Another armed reconnaissance mission was scheduled for March 6 or 7, but was canceled because of the delay in launching the first raid, damage to Hashizume's airplane, and the aircrews' exhaustion.

A followup to Operation K was to have commenced on May 30, but with French Frigate Shoals revealed as a possible IJN rendezvous point, naval patrols were increased under Admiral Chester Nimitz

Chester Nimitz

Fleet Admiral Chester William Nimitz, GCB, USN was a five-star admiral in the United States Navy. He held the dual command of Commander in Chief, United States Pacific Fleet , for U.S. naval forces and Commander in Chief, Pacific Ocean Areas , for U.S...

's command. A Japanese submarine spotted two American warships at anchor there (with two navy seaplanes scheduled to arrive the next day), prompting a cancellation of the plan.

A side effect of this increase in patrols was the IJN's inability to effectively spy on US naval activity (and the position of the US carriers). A Japanese submarine patrol line in was put into place on June 3, but the American fleet had already departed Pearl Harbor, on its way to fight the Battle of Midway

Battle of Midway

The Battle of Midway is widely regarded as the most important naval battle of the Pacific Campaign of World War II. Between 4 and 7 June 1942, approximately one month after the Battle of the Coral Sea and six months after Japan's attack on Pearl Harbor, the United States Navy decisively defeated...

.

The raid did have an effect on U.S. Navy morale. Nimitz's chief of intelligence, Captain Edwin T. Layton

Edwin T. Layton

Edwin Thomas Layton was a Rear Admiral in the United States Navy.-Career:...

, whimsically suggested one of Commander Rochefort

Joseph Rochefort

Joseph John Rochefort was an American Naval officer and cryptanalyst. His contributions and those of his team were pivotal to victory in the Pacific War....

's men, Wilfrid J. "Jasper" Holmes, had planned the attack, since it closely followed a story he had written for the Saturday Evening Post before the war, "Rendezvous". Holmes was exonerated.