Why weren’t the Japanese boats effective?

Japanese submarines were not nearly as effective as the boats in other navies. That was more an issue of philosophy and deployment, although there were some design flaws.

There were some shortcomings with the boats themselves. Japanese submarines were not designed to go as deep as others. The deepest they were designed for was 100 meters or about 330 feet. They were also noisier than our boats and easier to track. Japanese boats were usually larger and would naturally be less maneuverable, particularly when submerged.

The biggest operational failures for Japanese submarines were not locating the American carriers before the attack on Pearl Harbor, again before the Battle of Midway and yet again before the Battle of Leyte Gulf. In each case, the submarines arrived too late to spot our forces.

Submarine warfare was not highly thought of by the Japanese, either offensively or defensively. Escort duty did not help an officer’s career. Japanese submarines did not get radar until June of 1944, about two years after most American boats were getting theirs. The Japanese did not take anti-submarine warfare seriously until 1944 when it was too late.

However, the biggest issue was how they were used. Japanese boats were envisioned to be “fleet boats”. They were expected to operate with the fleet. Their job was to use their scout planes to locate the enemy fleet and inflict damage before the big gun battles.

NOTE: At first, we also thought of our submarines as fleet boats. But that wasn’t practical. Our submarines couldn’t keep up with most of the fleet. Even if they did, submarines would give away their greatest advantage – stealth. Perhaps, in this regard at least, we were fortunate that, after the attack on Pearl Harbor, there wasn’t much of a fleet for our submarines to operate with. Out of necessity, our strategy and tactics had to change.

“And it was the Japanese Navy’s repeated use of submarines for purposes for which they were not designed that was a major reason for the failure of the submarine force to achieve a creditable combat record.” (“Submarines of the Imperial Japanese Navy” by Dorr Carpenter and Norman Polmar, Naval Institute Press, 1986, page 11.)

It certainly seems a bit strange that the Japanese Navy, which used aircraft carriers so effectively in the early days of the war, was still designing submarines to participate in an expected “Kantai Kessen,” the decisive big gun battle to determine the outcome of the war.

Japanese tactics also left much to be desired. Captains were only allowed so many torpedoes depending on the target. They stationed submarines at specific intervals when creating picket lines, trying to interdict our fleets. Their locations became too predictable – if you found one you could easily locate the rest. This last issue may help explain how the destroyer escort USS England (DE-35) was able to sink so many Japanese submarines in a few days.

Japan had done some exercises to determine whether their submarines could be used as commerce raiders.  “Curiously, when Japanese submarines were exercised against merchant targets, they were found to be effective. However, not only was this lesson not heeded with regard to the employment of Japanese submarines, neither was the converse possibility, that enemy submarines could cripple Japan’s seagoing commerce.”  (“Imperial Japanese Navy Submarines 1941-45” by Mark Stille, page 6.)

As the war went on, and the U. S. began to push the Japanese back to the west, they began to use the boats more often as supply transports. Beginning in November of 1942, the Japanese were using some of their submarines to supply troops in outposts that the U. S. had simply bypassed in the island-hopping strategy. This was not a good use of submarines even if they did the job well. The Japanese air base at Yap might be a good example of this. American planes regularly attacked the Japanese airfields at Yap by carrier aircraft, but the island was never invaded. It was just left isolated and the Japanese decided to deliver supplies.

Submarine captains didn’t help themselves either. Reports are that they were very chatty, sending messages often. They also had a tendency to fire a few parting shots at American facilities as they were leaving or passing by. All of this made their boats easier to track.