The XXI was not the fastest sub during WWII!

Originally Posted by iambecomelife

4 torpedo tubes and 10 torpedoes is a very impressive armament for such a fast submarine. Also impressive that they managed to complete it long before the Type XXI and Type XXIII subs were built in Germany.
If the Japanese had gotten their act together and conducted a full-blown submarine campaign against shipping in the Pacific, WWII would have been quite different.

Not quite so. By Feb 1945 over 100 advanced Type XXI were commissioned, training or running trials. The Japanese completed two. Although only one Type XXI, U-2511 actually conducted a war patrol, none of the advanced Japanese subs managed to do so.

Besides 14 torpedoes was the capacity of the Type VII and generally analysed as being woefully inadequate for commerce warfare. Fleet boats carried 24 and Type XXI, 23. Nothing to see here.

Japan was cursed by geography, there were no American strategic maritime choke points for merchant shipping that could not be dominated by US air power. Therefore the IJN would have had all of the operational problems faced by the U-Boats exacerbated by much greater distances, a lack of doctrine and training coupled with submarines ill-suited to commerce warfare. There was never any real prospect of an effective Japanese tonnage war.

Cdr Paul Schratz, USN in his book Submarine Commander devotes an entire chapter to the I-201 class, he commanded one of the two captured boats on a one-way trip to Pearl Harbor where it was studied and then expended as a target. Having first hand experience with the class, his impressions are far less gushing and awe-struck than those here.

The Long Lance was a 24" surfaced launched torpedo, they were not used in submarines. The submarine Type 95 was O2 powered like the Long Lance but packed far less punch due to its smaller diameter (21"). The single salvo from I-19 that sank Wasp, O'Brian and damaged North Carolina was undoubtedly the most damaging single torpedo salvo of all time.

However since neither O'Brian or North Carolina were actually intended targets, it says more about sheer luck than any inherent Japanese weapon, fire control or training superiority.

One thing about the Internet is that people tend to go gaga over military technology for its own sake without ever considering the economic, operational, doctrinal, logistical and even cultural aspects of introducing that technology into service.