Operation K

Less than three months after the gigantic Japanese aerial and submarine onslaught against Pearl Harbor a second, considerably more modest, raid on the US Pacific Fleet’s anchorage was mounted by the Imperial Navy. Although nothing more than a ‘nuisance raid’, the logistical planning required to strike once again at American soil demonstrated the excellent Japanese use of aircraft and submarines working in close cooperation. Submarines were destined to play a crucial role in the operation, codenamed ‘K’, and much more effectively than the suicidal midget submarine attacks of December 1941.

The Japanese devised a plan to use a pair of newly introduced Kawanishi H8K1 four-engine naval flying boats of the 24th Air Flotilla to strike Oahu.7 These aircraft, given the codename ‘Emily’ by the Allies, had a maximum range of 3,040 miles and were able to haul one ton of bombs. They were a Japanese equivalent of the famous British Short Sunderland, though larger (incidentally, before the war the Kawanishi company had had a close working partnership with Belfast-based seaplane manufacturers Short Brothers). The plan would see both of these huge aircraft, each with a crew of ten, fly from a starting point at Wotje Atoll in the Marshall Islands to a midway point and rendezvous position at the remote French Frigate Shoals located 482 miles from Pearl Harbor. The submarine I-9 was ‘assigned to take up station midway between Wotje and the Shoal and act as a radio beacon’8 for the two flying boats. At French Frigate Shoals the pair of flying boats would meet two large Japanese submarines that would be waiting for them inside the protected lagoon. The two submarines selected for the primary part of the mission were the I-15 and I-19 respectively, both boats normally being fitted with the tiny two-seater Yokosuka E14Y1 floatplane for reconnaissance in a watertight hanger in front of the conning tower. For the purposes of Operation K the planes were removed and replaced with ten tons of aviation fuel in drums on each submarine, packed inside the hangar space for safe transit to French Frigate Shoals. After the arrival of the flying boats the two submarines would replenish the planes’ fuel tanks before the Kawanishi’s set off on the final leg of their outbound mission to Oahu. As a backup, should either of the two submarines be lost, the I-26 was directed to shadow the pair and act as a reserve fuel tanker, and also to act as a picket to constantly scan for any enemy activity in the vicinity.

The submarine I-23, under Lieutenant-Commander Genichi Shibata, had a more hazardous task to perform, which required her to creep as close as ten miles from the coast of Oahu and report on weather conditions over the target. Additionally, should either or both of the flying boats be shot down during the run over Pearl Harbor, the I-23 was to attempt to rescue any downed aircrew.

The Kawanishi H8K1 was also nicknamed the ‘Flying Porcupine’, and for good reason. Mounted in turrets and blisters around the aircraft were five 20mm cannon and four 7.7mm machine guns, making it a dangerous quarry for any roving Allied fighter to tackle. A pair working in close cooperation, and covering one another with their guns would be more concerned about ground anti-aircraft fire than fighter interception.

The Japanese selected 1 March 1942 as the day of the attack, and all submarines taking part in the operation were expected to be in position one day before the flying boats showed up. The I-15 and I-19 sailed imperiously into the lagoon at French Frigate Shoals at the assigned time, deck-guns fully manned in case American lookouts or coast watchers had been planted on the islands. Lieutenant Toshi Hashizume and Ensign Tomaro had been selected as the pilots of the respective Kawanishi’s, and they departed from Yokosuka harbour in Japan on 15 February and began the long journey to the mission jumping-off point. The flight plan took them first to Saipan in the Marianas, then the big Japanese naval base at Truk in the Carolines, and on to Jaliut in the Marshall Islands before they splashed down at Wotje Atoll. Weather was the all-important factor determining when the mission actually began, and information about the weather over Oahu came to the Japanese from two different sources. Firstly, they had cleverly cracked the local weather reporting code used by US naval air stations at Midway Island, Hawaii and Johnson Atoll. The second source would come from the submarine I-23, positioned ten miles to the south of Oahu. Unfortunately, just as the Japanese were gearing up to launch the mission all information concerning weather ceased. Two things had occurred which meant a delay in launching the aircraft on their way to Pearl Harbor. The first was a routine change in the code being used by the US Navy to report weather conditions over their airfields in the region, leaving the Japanese outside of the information loop. The other was the sudden loss of contact with the I-23, Radio communications emanating from the Japanese were also being picked up by the Americans, indicating to them that there was Japanese submarine activity in the area of French Frigate Shoals, ‘…so the Americans, centered on the Naval Combat Intelligence Unit at Pearl Harbor, broke Japanese naval codes, enabling them to ascertain the whereabouts of Japanese surface and submarine assets’.9 The sudden loss of contact with the I-23 was ominous, and, according to Hackett and Kingsepp, the Japanese Navy presumed the submarine lost with all hands on 28 February off Hawaii.

One of the principal Japanese naval bases in the Western Pacific, located at Rabaul in New Britain, now found itself menaced by an American naval task force that was discovered to be steaming towards the base as weather reports ceased, and the mission began to look in doubt. The task force, built around the aircraft carrier USS Lexington, appeared a juicy target to the Imperial Fleet’s local headquarters at Truk, and all available submarines and surface warships headed out and searched for the force. The two days spent on attempting to locate and attack the American task force, which aborted a projected attack on Rabaul, meant that the Pearl Harbor raid itself was delayed until 3 March. In the early evening the two big flying boats touched down safely in the lagoon at French Frigate Shoals, and the crews of the I-15 and I-19 set to work refuelling the huge beasts. At 9.38 p.m., both aircraft had lifted off and turned towards Pearl Harbor, the crews readying themselves for the daring strike against a location still clearing up the detritus and wreckage from the first Japanese raid, and a place maintaining a much better surveillance of the skies and seas around Hawaii, determined not to be caught out again by a sudden ‘surprise’ attack.

US Navy intelligence officers had spent the remainder of 3 March pondering the significance of Japanese submarine activity at French Frigate Shoals that had arrived on their desks from the decrypts of Imperial Navy radio communications. The officers remained unsure as to what it signified, and more importantly, whether such activity posed a threat to local American forces. The massive raid of 7 December 1941 against Pearl Harbor had been launched from Japanese aircraft carriers, and none were believed to be near to Hawaii in March 1942. No land-based Japanese aircraft had the range to reach Hawaii from the furthest regions of the Japanese Empire, and although the officers were aware that some of the larger Japanese submarines certainly mounted a small plane onboard, they also knew that the aircraft was essentially a harmless reconnaissance model that they had codenamed ‘Glen’. For the moment, the reports of enemy submarine activity remained routine, and no alarms were raised or the alert status at Pearl Harbor brought up a notch.

The pair of Kawanishi flying boats continued to devour the miles between the Shoals and a blacked-out Oahu, oblivious to the radar beams that constantly scanned the skies around the Hawaiian Islands. A US Army radar station at Kauai was the first section of the airborne early warning system to record a possible problem. At 12.14 a.m. on 4 March the radar ‘painted’ a single target moving towards Oahu at a range of 240 miles. The soldiers immediately informed the Air Raid Defense Center, who in turn telephoned the local Army Air Corps and US Navy air stations throughout the islands requesting that any friendly aircraft airborne be reported to the centre, and so could be eliminated from the air defence equation. Both the army and the navy replied that they had no aircraft then airborne, so the unidentified radar target was deemed most likely hostile.

Unlike on the morning of 7 December 1941, this time the Americans responded quickly and efficiently to the threat they now perceived to be fast approaching. At 12.43 a.m. the air defence commander ordered general quarters, bringing all military and civil defence personnel to full readiness of an impending air raid on Oahu. At 1.15 a.m. a trio of US Navy PBY Catalina flying boats took off with orders to seek out any Japanese aircraft carriers lurking close to the islands that would explain the presence of enemy aircraft bearing down on Pearl Harbor. Four Curtiss P-40 Warhawks formed local air defence, and these fighters were scrambled at 1.36 a.m. to form a Combat Air Patrol (CAP) over Pearl Harbor with orders to intercept and shoot down any hostile aircraft encountered. This was easier said than done, as the Americans lacked any dedicated night fighters, and as the P-40s were bereft of radar the pilots would have to hunt by following ground directions and using their eyes. Although originally the night had been clear, with a full, bright moon, the weather had rapidly deteriorated, and rain and clouds were now building up over the intended Japanese target. The rain that would prevent the P-40s from discovering the Japanese flying boats that night also prevented the two amphibious bombers from satisfactorily locating their targets.

The two pilots, Hashizume and Tomaro, planned to deposit their bombs over the central Ten-Ten Dock at Pearl Harbor, but as the two Japanese planes made landfall at the extreme western tip of Oahu and headed inland across the Koolau Mountains at 15,000 feet, both pilots noticed the clouds and rain squalls building up ahead of their machines. The Japanese planes stuck to an easterly course that would take them to the north of Pearl Harbor. Once close to the harbour the amphibians would make a sharp turn to port and head south to begin their bombing runs over the base. Lieutenant Hashizume’s aircraft followed the set course and arrived over the harbour as planned, but the target was badly obscured by cloud cover. Some members of his crew yelled over the intercom that they had seen Ford Island in the centre of the Pearl Harbor naval base through breaks in the cloud, but Hashizume decided to fly on, make a turn, and come back for a second look before releasing his bombs. The pilot banked the huge aircraft round to port and started back for his bomb run, dropping his payload at 12.10 a.m. through the clouds. These bombs rained down on some trees carpeting the slopes of Mount Tantalus behind Honolulu, six miles from Pearl Harbor. Four booming explosions echoed off the hills to mark the arrival of the Japanese, though hardly a soul registered the detonations as having a Japanese origin.

The second aircraft, with Ensign Tomaro at the controls, did no better than Hashizume. When Hashizume had made his sharp turn to port designed to bring him back over the target, Tomaro had misunderstood Hashizume’s order and had carried on following the southern route. Realizing his mistake with the disappearance of his wingman, Tomaro hauled the big flying boat around and retraced his path back north. At 12.30 a.m., unsure of his exact position but believing himself to be over Pearl Harbor, Tomaro released his bombs, which fell harmlessly into the sea. Both Kawanishi’s now formed up and headed away from the islands with all possible haste, leaving the P-40s and Catalinas to search fruitlessly for them.

Hashizume’s aircraft had completed the mission with a punctured hull, and this aircraft headed straight for Jaluit for repairs. Tomaro took his plane to Wotje Atoll, arriving at 2.45 p.m. Both pilots wrote detailed reports of their sorties over Oahu, and both men concluded correctly that the level of damage they had inflicted on the naval base was difficult to determine, owing to the weather conditions they had encountered over the target. Back at Pearl Harbor, to begin with the four explosions that had been heard on Mount Tantalus were investigated. The Americans initially thought that one of their own aircraft from either the army or the navy had dumped its bomb load in the countryside before landing, but closer examination of bomb fragments recovered from the scene revealed them to be of Japanese manufacture. An even more extraordinary answer to the riddle of how the Japanese had carried out the daring long distance attack slowly revealed itself, an interesting case of life imitating art.

American intelligence had suppressed a short story written by a serving naval officer in 1940 entitled Rendezvous.10 The story, by W.J. Holmes, then a lieutenant, told of a fictional American raid on a Japanese base. In the story, the Americans plan to bomb Japanese preparations for an amphibious operation by using flying boats. Because the flying boats lack the range to reach Japan from Hawaii, three submarines are used to refuel the aircraft at the fictional ‘Moab Atoll’ located 1,000 miles from Japan. The American submarines carried not only aviation fuel for the thirsty flying boats, but the bombs that they would drop on the mythical port of ‘Bosoko’ in the raid. The Office of Naval Intelligence had suppressed the story in November 1940, but after Holmes defended his right to publish using examples of similar British and Italian seaplane operations, the navy relented and Rendezvous appeared in the August 1941 edition of the Saturday Evening Post. Following the Japanese raid on Pearl Harbor in March 1942, Rear-Admiral Edwin Layton, chief intelligence officer to the commander-in-chief of the US Pacific Fleet, Admiral Chester W. Nimitz, disclosed that the Japanese had most probably copied the idea for the raid from Holmes’s short story, supplanting ‘Moab Atoll’ for the very real French Frigate Shoals as a refuelling waypoint. In the story Rendezvous the Americans manage to wreck the Japanese ships assembling in ‘Bosoko’ harbour for an amphibious attack. In the real mission, the Japanese failed to cause any damage, apart from digging up some trees.

The Americans looked carefully at Holmes’s story, and decided in light of the recent attack to dispatch the destroyer USS Ballard to the French Frigate Shoals to take a careful look, and leave behind some mines should any Japanese submarines have returned. They never did, and the evident failure of so complex an operation, including the use of three fleet submarines that would have been better employed elsewhere, meant that the Japanese would not attempt another operation of this sort again.

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