This is the "second K-war", the early reconnaissance work of the Japanese army fighting for Midway Island. It is said to be the "second time" because1March 942, the Japanese army conducted a "K War" with almost the same process. At that time, the Japanese army took off two Type II flying boats (large seaplanes with a long voyage) of Yokohama Air Force from Kwajalein Atoll in Marshall Islands, which it occupied, and secretly conducted night reconnaissance and air raids on Pearl Harbor. Because of the long voyage, the Type II large boat docked at Francci Riegert Atoll (literally translated as French frigate atoll) to be refueled by the Japanese submarine that arrived here ahead of schedule-the seaplane can be moored on the calm sea, and then the submarine can surface and refuel it through refueling equipment. After refueling, two two-type large boats continued to fly to Pearl Harbor to perform their tasks. On that day, the meteorological conditions in Pearl Harbor were not good, so although the US military radar found suspicious planes, it failed to capture and intercept the two Japanese planes. However, Japanese planes are also plagued by bad weather and cannot detect any valuable information. In the end, it had to drop the mounted bomb as estimated and then return to Kwajalein Atoll. This is the process of the first "K War".

The "Battle of K" was the second Japanese air attack on Pearl Harbor, but it is estimated that the bombs dropped did not actually hit any targets, and some simply fell into the sea. The biggest "loss" was breaking the window of a school ... but this air raid still aggravated the already nervous fear of Japanese invasion in Hawaii. In addition, it is worth mentioning that when the US military analyzed the relevant telegrams of the Japanese army about this operation afterwards, it was found that the seaplane performing the task should be alert to the US military reconnaissance from the AF direction on the way. According to the route of the Japanese military, the "AF" under the control of the US military that is most likely to make them vigilant is midway. This provided the first breakthrough for the US military to solve the mystery of AF before the Battle of Midway.

Before the Battle of Midway Island, the Japanese army planned to repeat the old trick and reconnoiter Pearl Harbor with two large boats again to confirm whether the main force of the US Pacific Fleet was still in the harbor. The operation was originally scheduled for May 30th, but the US military has raised its vigilance and sent a seaplane supply ship to Francci Riegert Atoll in advance, turning it into its own seaplane base. As a result, when the Japanese submarine preparing to refuel the Type II large boat arrived at the atoll, it was found that the US military had boarded first, which made it impossible for the Japanese army to refuel its seaplane in the atoll as planned, and the "Second K War" was forced to be postponed for one day. After waiting for a day, the Japanese submarine found that the American army had no intention of leaving, so it completely canceled the reconnaissance of Pearl Harbor. If the Japanese reconnaissance plane flies to Pearl Harbor at the end of May, they may find that there is no aircraft carrier moored in the harbor (the US military task force 16 and 17 went to Midway Island on 29th and 30th respectively). In any case, the failure of the "Second K War" and the subsequent delay of the Japanese submarine warning line due to insufficient preparation (originally scheduled to be in place on June 2, it was actually not in place until June 4, when the American aircraft carrier had already passed the scheduled sea area), which laid the groundwork for the defeat of the Japanese midway island. But on the other hand, we should also see that both Yamamoto and Nan Yun received reports of the failure of the "Second K War", but the Japanese commanders did not raise their vigilance because the reconnaissance work was not in place.