You know, Japan’s devastating attack on Pearl Harbor, Hawaii. It was Dec. 7, 1941. 

But what about March 4, 1942, the second time Pearl Harbor came under Japanese attack? 

It’s true. Less than 90 days after that infamous Sunday morning surprise assault, Japanese bombs again fell on Oahu. Though far less lethal than the first round, the second strike was considered too hot for the American people to know about at the time. It was kept secret for decades.

This is the story of Operation K.

Japan’s Imperial Navy had scored a spectacular victory with the first bombardment. Though not a complete success (because the biggest prize of all, the Pacific Fleet’s three aircraft carriers, were at sea), it was still a crippling blow. Four battleships were sunk. Four others were severely damaged. Nearly 200 warplanes were destroyed, with another 159 disabled. Eleven other ships were sunk or badly harmed. Even worse, 2,335 service members and 66 civilians were killed. Another 1,178 were wounded.

Japanese military planners turned their attention to bigger targets. They wanted to use long-range Kawanishi H8K flying boats to bomb California and Texas. But first, they needed to know how repair operations were going at the important base’s naval docks and airfields.

The mainland attack was sidelined for a new scheme. Five flying boats would make a reconnaissance flight over Pearl Harbor and also drop a few bombs while there.

The night of March 4 was selected because its full moon would provide visibility. The flying boats would land at French Frigate Shoals, the northwest Hawaiian Islands’ largest atoll, and be refueled by submarines. Then, they would be off to Pearl Harbor.

As the attack neared, history repeated itself in more ways than one. Just as had happened before the Dec. 7 attack, American intelligence picked up clues something big was about to happen. Incredibly, the warnings were once again ignored.

Things began badly for the Japanese. Only two flying boats were available, not the five as planned. Each was loaded with four 550-pound bombs. Freshly refueled, they took off from French Frigate Shoals and headed for Oahu, some 560 miles away.

The clear skies they were counting on disappeared as a thick cloud cover rolled in. That meant that while American defenders on the ground couldn’t see the flying boats, the flying boats couldn’t see the ground, either.

Those clouds also confused the Japanese pilots, who were supposed to attack in tandem. However, the second flying boat didn’t hear the orders coming from the first and they went their separate ways.

Squinting through the murky night, it was impossible to see anything. So the planes dropped their bombs when crewmen guessed they were close to their targets.

The first fell on a mountainside near Roosevelt High School, creating deep craters and shattering nearby windows. Nobody was hurt. It’s believed the second plane’s bombs fell in the Pacific Ocean.

Thanks to the wartime blackout, the pilots couldn’t use lights to guide them off the island. Both planes eventually landed at different airbases on the Marshall Islands.

What did Operation K produce? Not much beyond showing that Japanese warplanes could still penetrate Hawaiian airspace. While the American army and navy blamed each other for the mysterious nocturnal explosions, the Japanese were planning another intelligence run for March 6 or 7. But exhausted crews and damaged planes postponed it to May 30.

By then, Tokyo was desperate to learn the whereabouts of the U.S. aircraft carriers. But it was too late. The Americans had finally wised up to French Frigate Shoals use as a refueling site and rushed warships to the area. The Japanese reluctantly scrapped their plans.

As a result, they had no idea that the U.S. carriers were secretly rushing toward what would become the decisive Battle of Midway, which stopped Japan’s offensive in its tracks and set Americans on the long road to victory.

That story might have ended differently if Operation K’s attempts to put an eye in the sky had succeeded.

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