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December 1980

Downfall Of: The I-Boats

The Emperor's subs were used in the wrong place, at the wrong time and for the wrong reason

By Edwin P. Hoyt

On the night of December 6, 1941, a dozen Japanese submarines lay in two long arcs southeast and southwest of Pearl Harbor. Five other submarines moved silently toward the harbor entrance, each of them carrying a midget two-man submarine that would be used in the actual attack. All the large subs were of a class called the I-Boat, superior in range and firepower to the best American submarines of the Pacific Fleet.

The mission of the dozen submarines in deep water was to watch for units of the American fleet--particularly the U.S. carriers--and torpedo them. Fourteen other Japanese submarines ranged north of Oahu island and were given the same mission, plus the extra tasks of reporting on weather for the combined fleet and serving as "lifeguards" to pick up any pilots shot down at sea after the December 7th attack. Still other submarines were moving along the west coast of the United States.

At six o'clock the next morning, the two-man crews of the midget submarines entered their small craft, and were soon released by the I-Boats within striking distance of the entrance to Pearl Harbor. They began to move forward, but almost immediately there was trouble: the American destroyer Ward, patrolling the area just off the Pearl Harbor entrance buoys, detected the sound of the small electric motors and launched a depth charge attack. A charge struck close enough and one Japanese midget submarine never resurfaced.

This same fate befell the other four midget subs. One of them managed to get inside the harbor, apparently following in the wake of a patrol boat or tender. But once the attack from the air was launched and the harbor was alert, the seaplane tender Curtiss opened fire on the midget and the destroyer Monaghan rammed it.

Such misadventure plagued the entire wartime effort of the Japanese submarine force, with a few notable exceptions. In January 1942, an IBoat torpedoed the carrier Saratoga about 500 miles southwest of Pearl Harbor, but she survived to fight again. 1-168 sank the crippled carrier Yorktown at Midway. In the Solomens, submarines sank the carrier Wasp and damaged the battleship North Carolina and the destroyer O'Brien. There were other sinkings of American warships up to the very last days of the war including the cruiser Indianapolis which went down after being torpedoed by 1-58. So the Japanese had the weapons: excellent submarines (23 knots on the surface), excellent torpedoes and well-trained crews. Yet with the few notable exceptions indicated above,  the Japanese submarine service played a very small role in the Pacific War.

Part of the reason was the strategic concept of the Japanese high command which went back to an early theory of the application of submarines to warfare. In the beginning, submarines were regarded as useful for scouting and for attacks on enemy warships. The Japanese never got beyond that concept. The sort of thinking that led the Japanese high command to spend millions of yen on midget submarines also caused them to ignore the most valuable role of the submarine, that of commerce raider. On Pearl Harbor day, I-16 was not far from Seattle and she sank a merchantman. But Commander Minoru Yokota had been sent to the area primarily to check out American strength in the Aleutian Islands area against a surprise counterattack. The sinking of the merchant ship was incidental.

Later, the long-range Japanese I-Boats would be used to shell Santa Barbara, CA. An I-Boat launched a plane from French Frigate shoals that confirmed the extent of the Japanese destruction along Pearl Harbor's battleship row. Two other I-Boats fueled the long-range Japanese bombers that set off from French Frigate shoals in March 1942, to make the "second bombing of Pearl Harbor." But all this was military endeavor against military targets and not the commerce raiding for which the American submarines became so famous. Had the Japanese employed their submarines properly, they might have prevented the rebuilding of Pearl Harbor for months. They might even have cut off Australia.

The Japanese insistence on using submarines as a fleet force was all the more remarkable in view of two Allied developments that greatly decreased their effectiveness. The first of these was radar, which the I-Boat force encountered in June 1942, when the 1-5 was nearly sunk in the Aleutians on a day so foggy that nothing could be seen 20 feet away. 1-5 was on the surface traveling dead slow when suddenly the boat was surrounded by exploding shells. She crashed dived just in time to be saved.

The second development was the radio direction finder. Given three points (one of which might be a vessel at sea) a radio receiver could concentrate on radio beams and operators could triangulate and, thus, pinpoint the location of a submarine at sea. As the war progressed and the Pacific Fleet radio intelligence organization grew, locating Japanese submarines at sea became a major activity.

The Japanese submarine effort, of course, was hardly helped by the course of the war. After the Americans attacked Guadalcanal in the summer of 1942, the Japanese began winning the naval war of the South Pacific hands down. But, as the Americans brought more warships equipped with radar into the area, the odds began to change. When the U.S. fighter plane force was increased, the Japanese began to sacrifice the air superiority that had made so much difference. Yet this should not have wiped away the effectiveness of the Japanese submarine force and it did not.

On November 13, 1942, as the battle raged, the I-26 sank the cruiser Juneau, which blew up with most of her crew. The real difficulty was the stubborn American refusal to be defeated at Guadalcanal when the Japanese bad superiority, and the decision made by the Imperial High Command that submarines would have to be used to supply and ultimately evacuate the troops in the Solomons.

One of the most effective weapons of the Americans was the Naval Combat Intelligence Unit functioning at Pearl Harbor. By the autumn of 1942, the combat intelligence men were reading the Japanese codes. They could tell when forces were building up at Truk or Rabaul to reinforce Guadalcanal. Taking advantage of this information, ships, planes and submarines were warned and attacks were launched. Time after time this technique was successful to the degree that by November 1942, Japan began building enormous transport submarines to work with submarines pulling long tubes filled with extra supplies bound for Guadalcanal.

Island by island, the Marines and soldiers of the Central and South Pacific forces pushed the Japanese back. The intensified American campaign and the buildup of Allied air power made the difference. Between late 1942 and September 1943, the Japanese submarines made 100 trips to New Guinea just delivering supplies.

Then, early in 1943, a new American weapon appeared in the South Pacific: the destroyer escort. At the beginning of the war the Americans had no warship smaller than a full fledged destroyer, save a few old relics such as the Eagle boats of times past. The admirals did not believe in small vessels, But the U-Boat war in the Atlantic soon showed them that the small, anti-submarine, escort ships were extremely effective.

The Japanese submarines began to fall victim to the DE's and the Australian corvettes. The HMAS Kiwi fought, rammed and sent I-1 aground at Guadalcanal, and half a dozen DE's sank or mauled Japanese submarines in the area. But the most effective destroyer escort of all was USS England, which in her own way changed the course of the Pacific war.

Had Admiral Yamamoto survived the South Pacific war, the course might also have been different, for Yamamoto was a brilliant strategist, But he was entrapped (by American radio intelligence), ambushed by American planes and died in the crash of his plane. He was succeeded by Admiral Mineichi Koga, who lacked the Yamamoto flair. Then, in the spring of 1944, with the Marianas campaign looming, Koga was killed. The command passed to Admiral Soemu Toyoda, who had little experience in high position.

One of Admiral Toyoda's major concerns was intelligence. The Americans had taken the Gilberts and the MarshalIs and were ready to move again. But where? Before, in the better days, the Japanese had been able to scout the enemy with aircraft, but most of the air scouts who went out that spring did not return. The next assault could be on the Philippines. Or it could come to the Marianas. Toyoda had to know, so he did the only thing he could: he sent a scout line of submarines to take sentry duty along the routes the enemy might advance. Admiral Takeo Takagi, commander of the submarines' Sixth Fleet, sent a dozen submarines out to scout. It was indicative of difficulties the fleet was suffering that only one of these was equipped with radar.

On May 16, I-16 left Truk. She had nothing to do with the scouting force, but was carrying supplies to Japanese troops stranded on Bougainville. She was spotted by American aircraft and the fleet was warned. Three American DE's were sent from the Solomons to intercept. The England found I-16 and, after a brief attack, sank her.

Less than a week later, England was cruising in the same general area when she ran across R0-106. a smaller submarine which had been pressed into service for this picket line operation. After a brisk attack, R0-106 went to the bottom. By this time, the Americans had a pretty good idea of the Japanese strategy and they were looking out for just such a picket line. England moved west a few miles and discovered R0-104, the next picket submarine. The American DE was operating with two others, USS George and USS Raby. That day, R0-104 managed to elude their combined attack. But the following day, England found her again and sank her.

The next submarine in the picket line was R0-116 and it was only a few hours later that she, too, was sunk. A day later, England sank R0-108. A few more hours passed and she sank her sixth submarine, R0-105, for a new world's record: six submarines in 12 days.

The Chief of the Japanese Combined Fleet was waiting for information. Where the Americans were going to attack was still in question. To meet that attack, Admiral Toyoda was committed to the A-60 plan which was supposed to be that last great battle in which the Japanese would wipe out the American fleet.

The word that six of his picket submarines had been sunk in less than two weeks convinced Toyoda that the attack was coming against the Philippines. Therefore, he concentrated his forces in the south and did not send them east where they might have disrupted the Marianas attack before it got well started. The England, then, can be credited for success far beyond the call of duty in her remarkable exploits against the Japanese submarine fleet.

In the latter days of the war, the Japanese submarines were further reduced to moving troops into and out of impossible situations. During the heat of the Marianas campaign, one submarine was used to take 50 downed fliers from Guam so that they might fight again. Admiral Takagi, the submarine commander who had moved his headquarters to Saipan to better manage the submarines, was to be rescued at the end of the campaign by one of his own vessels. The submarines had become a high-level supply and ferry service, but it did not always work so well. 1-10, sent to rescue Takhgi, was sunk and the admiral committed suicide on the night of the last great battle, a victim of the overwhelming might of the American forces. His epitaph could well be that of the entire Japanese submarine service in World War II: He died in the wrong place at the wrong time for the wrong reason.

That was how it went with his Sixth Fleet, almost from the day they planned the Pearl Harbor attack.