Two Kawanishi H8K Emily flying boats may not seem like a lot of firepower in our day of jet power, stealth, and super-cruise capability. But back in 1942…well…it wasn’t much firepower then, either.
But that’s what the Japanese could spare, and it’s what they used to carry out “Operation K”, their second attack on Pearl Harbor, executed March 4, 1942. The two flying boats had stopped in the French Frigate Shoals to refuel the night before, then took off again, heading for their targets.
When they arrived, they found that they hadn’t achieved anywhere near the surprise of the December operation. The U.S. Navy was on a hair-trigger state of readiness to begin with. But cryptologists had also gotten wind of potential attacks through intercepted messages from the Japanese they had decoded. Furthermore, Hawaii radars picked up the incoming planes early and P-40 Warhawks had been sent aloft to engage.
Fortunately for the attackers, cloudy skies prevented the fighter cover from locating the flying boats as they flew in. Unfortunately for the attackers, cloudy skies prevented them from finding their targets. In the end, they dropped their bombs on nothing of consequence and made their escapes.
And while this seems like an insignificant incident, it really had far-reaching consequences. First off, it further verified that American code-breakers were accurately deciphering enemy messages. Second (and just as important), it tipped the U.S. Navy off to the fact that the Japanese were using French Frigate Shoals.
A month later, as code-breakers began to clearly see the plans for another major operation against Midway, planners deduced (correctly) that the Japanese Navy might try to make use of the French Frigate Shoals again. So they parked a seaplane tender out there.
Indeed, the Japanese had designs on the Shoals. Another plan, also called Operation K, was set up to allow float planes to refuel and then set out for Pearl, this time to report back on which ships left Pearl Harbor to head for Midway. As we know, this second Operation K was foiled, and its failure was one of the reasons the Battle of Midway was an unmitigated disaster for Japan.