Why Axis submarines could not readily share weapons

Could German and Italian submarines in the Indian Ocean use Japanese weapons?

Not readily; fire-control incompatibility and nonstandard machinery made both weapon integration and maintenance difficult.

Japanese torpedoes and German or Italian submarine fire-control inputs were unlikely to match without significant adaptation. Support was already difficult because nominally similar Type IX U-boats could require different engine spares after extensive individual modification. Shared bases did not erase national differences in weapons, machinery, and maintenance practice.