The Japanese had some of the heaviest, long-ranged and fastest submarines during WWII and they carried one of the finest torpedoes at the time: Type 95 oxygen torpedo (based on the Type 97 "Long Lance") yet they achieved little in part thanks to the use of an outdated naval doctrine:
In the "Kantai Kessen" doctrine, submarines were thought as scouts instead of commerce raiders. Their main task was locating, shadowing and attacking the enemy task forces with torpedoes. In 1942, Japanese submarines sank two fleet carriers, a cruiser, a few destroyers and some auxiliary ships. They also damaged two battleships, one fleet carrier (twice), and a cruiser. But as Allied intelligence, technologies, methods and numbers improved, they never achieved the same successes in the following years.
Japanese submarines weren't limited just by the "Kantai Kessen" doctrine: their commanders preferred engaging merchant ships with deck guns, which not only negated the element of surprise, but also made them much more vulnerable to enemy escorts (definitely not helped by the fact that Japanese submarines were large targets and slow to dive, given their size and overly complex linkages in their propulsion systems).
In total, Japanese submarines sank a total of 184 merchant ships of 907,000 GRT far less than achieved by the Germans (2,840 ships of 14.3 million GRT), the Americans (1,079 ships of 4.65 million tons), and the British (493 ships of 1.52 million tons).
American submarines on the other hand were much more successful, once naval doctrine and skippers were changed, and the deficiencies of the Mark 14 torpedo were adressed they sank almost 2/3 of the Japanese merchant fleet and over 200 IJN's warships, including six fleet carriers, three escort carriers, a battleship, twelve cruisers, forty-three destroyers and twenty-three submarines.
Morale amongst Japanese submarine crews was poor: the growing technolgical edge of the Allies didn't help, neither the employment of submarines to resupply isolated garrisons.
This is reflected in a post-war report prepared by the US and British Navies which states: "It was frankly impossible to believe that submarines could spend weeks on the US west coast 'without contacts,' or spend more than 40 days running among the Solomons during the Guadalcanal campaign 'without seeing any targets.'
Even the Japanese commanding officers could not disguise their embarrassment when recounting these tales. Further enlightenment is found in the extremely large number of times the target was 'too far away to attack.'"
US: You sunk three ships with one torpedo!! Sub: I did not mean too i just wanted to sink something Us: Helllllooooo You got triple kill Sub: okay i meant to
8 minutes later
One torpedo hit the USS North Carolina.A little history lesson: I-19's actions in the Solomon Islands
On that day I-19 managed to damage three American ships with a single torpedo salvo.19's awesomeness in an easy to understand formatAbout 10km ahead1km ahead
1 minute laterCarrier USS Wasp was sunk by three torpedo hits!! 7 minutes later
Destroyer USS O'Brien was sunk by 1 torpedo hit.
Although it didn't actually immediately sink the O'Brien but set up structural weakness that resulted in her splitting in two on the 18th of October 1942 and then sinking. However, I-19's battle records only contained the sinking of USS Wasp. She didn't know about O'Brien and North Carolina nor the fact that she managed to hit them. She has been called a sniper in the sea but it was just an accident.A meme related to Fukudome Kousuke. See also Tim Souers' blog.
