The December 7, 1941, attack on Pearl Harbor remains seared into collective memory as a moment of profound shock and tragedy, immortalized in history books and Hollywood epics alike. Japan’s surprise aerial onslaught crippled the U.S. Pacific Fleet, leaving thousands dead and several battleships sunk or badly damaged. Yet what many don’t realize is that Japan had a follow-up plan: a second strike dubbed Operation K.
This little-known operation aimed to hit Pearl Harbor once more, hoping to derail American salvage and repair efforts and keep the fleet out of action longer. But unlike the first attack’s precision and coordination, Operation K was beset by logistical hurdles and adverse weather, which conspired to doom the mission to failure before it could achieve any meaningful impact.
What did Operation K entail?
Operation K was set for the night of March 4, 1942, and was supposed to involve five massive long-range Kawanishi H8K flying boats. But because of logistical problems, only two aircraft were ultimately available for the mission.
These planes were originally earmarked for bombing runs against mainland U.S. targets like California and Texas, but first, the Japanese wanted to check on the repair progress at Pearl Harbor. The H8Ks were ideal for reconnaissance, and since each could also carry four 550-pound bombs, they had the ability to further disrupt the Pacific Fleet’s recovery efforts.
This mission was historic because it became the longest-distance bombing run ever carried out by just two planes, and it ranked among the longest bombing missions ever flown without fighter escorts. The round-trip journey from the Marshall Islands to Pearl Harbor and back covered more than 2,000 miles. To make this enormous trip possible, the Japanese placed fuel tanks at the French Frigate Shoals, where the flying boats could refuel before making the final 500-mile push toward their target.
Unable to approach Hawaii by sea
At first, the Imperial Japanese Navy viewed initial strike on Pearl Harbor as a major success. But soon after, aerial reconnaissance revealed that the U.S. Navy was recovering far faster than anticipated.
Determined to prevent another surprise attack, American forces quickly upgraded their offshore surveillance systems, making it extremely difficult for enemy vessels to approach Hawaii undetected. As a result, Japan shifted tactics, opting to send in long-range bombers for their follow-up strike. Their primary target was the Ten-Ten dry dock, where several damaged warships were undergoing repairs. By targeting these vessels, the Japanese hoped to stall the Pacific Fleet’s resurgence and buy the IJN more time to maintain its strategic advantage.
The operation was timed to coincide with a full moon, giving the pilots better visibility during their nighttime mission.
Kicking off Operation K
Before Operation K got underway, intelligence operatives monitoring Japanese activity noticed H8K flying boats preparing for the mission and alerted naval commanders on Oahu. Sadly, these warnings were mostly disregarded. Leading the operation was Lt. Hisao Hashizume in the first flying boat, with Ensign Shosuke Sasao piloting the second. The submarine I-23, tasked with relaying vital weather updates, had become lost days earlier, leaving the crews without accurate forecasts.
As the mission began, radar operators on Kauai detected the incoming aircraft, triggering a defensive scramble. U.S. forces launched PBY Catalinas and P-40 Warhawks to intercept the Japanese planes. Low clouds shielded the H8Ks from easy detection but also hampered visibility for both sides. A breakdown in communication between the two flying boats caused them to lose formation, throwing off their timing.
The lead plane’s bombs fell harmlessly on a hillside near a school in Honolulu, shattering a few windows but causing no casualties. Meanwhile, the second aircraft missed Pearl Harbor completely, dropping its payload into the ocean. Following the failed bombing, the two flying boats retreated to the Marshall Islands, each landing separately at different airfields.
What was the outcome?
The main result of Operation K was that the United States discovered that the Japanese could still enter its airspace and leave without being stopped. The US Army and Navy blamed each other for the nighttime explosions near the school. The mission also caused concern about possible more Japanese attacks on the US.
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Though a follow-up was planned for a few months later, it was eventually canceled because the Americans realized the Japanese were using the French Frigate Shoals as a base and had increased patrols in the area.