The XXI was not the fastest sub during WWII!

[mookiemookie]

Originally Posted by vanjast

If the IJN had a determined sub campaign.. they would caused crippling losses to the pacific task forces and invasion forces.
the wouldn't have to build their own subs, just buy them from the germans.

How would this have worked when German submarine production couldn't even replace their own losses in the Atlantic? How would the subs have been delivered? The only way to get them there would have been sailing them to Japan around Africa. Logistically, the idea would never have worked.