180° different than the hugely successful American submarine force, actually not much at all considering their potential strength/innovation, just some small, local victories/sinkings, and mostly its Admiral Yamamoto to blame:
“Overall, despite their advanced technical innovation, Japanese submarines were built in relatively small numbers, and had less effect on the war than those of the other major navies. The IJN pursued the doctrine of guerre d’escadre (fleet vs fleet warfare), and consequently submarines were often used in offensive roles against warships.
Warships were more difficult to attack and sink than merchant ships, however, because naval vessels were faster, more maneuverable, and better defended.”
Yamamoto sic’ed his submarine force on the Allies warships instead of the more essential tankers and supply ships. This chart tells the story pretty accurately:
