What Happened to the Japanese Submarine
To answer these questions, some historical perspective is needed.
In the early 1930s, Imperial Japanese Navy strategists became concerned about the accuracy of their torpedoes. When fired at long range, they would often miss. Their solution...develop a submarine that was small enough to approach enemy vessels undetected and close to such a close range that the torpedo could not miss. Prince Fushimi, then Admiral of the Fleet, embraced the concept and allowed two prototypes to be built with only one stipulation...that they be neither designed nor deployed as suicide weapons. From this simplistic concept was born the Japanese special submarine. Years later, when the plan for the “Hawaiian Operation” was firming up, Admiral Yamamoto, Commander-in-Chief of the Combined Fleet, was approached by submarine officers on his staff with a proposal to include the ultra-secret midget subs in the attack plan. Yamamoto would not consider it until plans were included to position fleet submarines at a pre-assigned collection point with the purpose of collecting the midget sub crews and returning them to base. After he had been assured that the midget submariners could effectively be recovered after a successful mission, Yamamoto became their greatest advocate. The naval aviators objected to the presence of the submarines from the outset, worried that premature detection of even one submarine would alert the defender's forces and ruin any chance for surprise (as events happened, this is exactly what almost happened). However, Yamamoto was unyielding...his concept for the operation included a multi-dimensional threat from which the U.S. forces could not escape. He insisted on including the special subs in, but not necessarily integrating them into, the overall attack plan. The submarine attack plan was developed separately from the aerial attack plan, with only one coordinating instruction...the subs could take no action that would reveal their presence before the aerial attack began at approximately 0800 local. Yamamoto insisted that the subs be recalled at any moment if it appeared that they could not be successful. He refused to sacrifice the midget submarine crews needlessly.
The concept, popular in the United States, is that from the very outset, the Japanese favoured suicide missions. This does not give credit to the commanders like Yamamoto who did not allow lives to be sacrificed needlessly. This is a practical consideration...it takes time and resources to train a pilot or submarine commander and a fighting force can only gain battle experience if the warriors live to fight another day. It wasn't until 1944-5, when Japan's back was to the wall and trained pilots were becoming scarce, that the Japanese military resorted to tokubetsu kogeki tai (often abbreviated to tokkotai), or "special attack units," where the attacker was deliberately sacrificed.
Returning our attention to 1941, the special submarine crews were well aware that they were to attempt to penetrate America's greatest fortress in the Pacific. Contrary to popular belief that American forces were asleep at the switch, the defenders on O'ahu were trained and as well prepared as could be to defend against an expected submarine threat. The skippers of the five special submarines selected for the mission knew that the odds of returning home safely was practically nil...even though theirs was not officially a suicide mission, in all practicality it was. Each submariner prepared final goodbyes to his family. They even joked about how they would go down literally swinging the sword that each carried aboard. Masaharu Yokoyama told his crewmate, Kichiji Dewa, that he would surface his boat and stand defiantly in the open hatch as he fired his last torpedo into the enemy. They prepared for death, but that does not mean that they were prepared to die.
After the war, Rear Admiral Hisashi Mito, Chief of Staff, Sixth Fleet (Submarines), was asked whether or not the midget sub crews were expected to return after the attack on Pearl Harbor. He responded:
While the probability that they would be able to return was very small, it was not thought to be wholly impossible. All midget submarine personnel, however, were prepared for death and none expected to return alive...none were recovered, though all possible recovering measures were exhausted.