Simon said:
Well it would of helped if the American Mark XIV torpedoes hadn't been so bad that as the official historian put it 'The only reliable feature of the torpedo was its unreliability' and the Bureau of Ordnance back home such a clusterfuck. It must have been supremely frustrating for the submarine captain. If they had been issued torpedoes that actually worked in the field then as you say the Japanese shipping fleet and economy could have been crushed much faster.
Supremely frustrating? You have no idea.

Skippers fulminated. (Morton, after a dry patrol, came back asking Lockwood for boathooks, if he wasn't going to get working torpedoes.

) At least one set up as near a live fire trial, against a Japanese ship in the war zone,

as you could manage, & had
fourteen consecutive failures.


BuOrd specialists sent out to investigate, on at least one occasion, sabotaged the torpedoes so they could blame the crews.

(All of this is recorded in Blair. Except maybe the boathooks remark...; it's been awhile since I've read it.

)
Faster, but not as much as you'd think, actually. The more important failure was a prewar fuckup in San Francisco. A Customs agent, whose name should be as infamous as Benedict Arnold's IMO,

seized & copied a Japanese merchant marine codebook. It was so clumsy, the Japanese couldn't help notice, & they changed it. At the time,
ONI was reading it.

It didn't get broken again until about January 1943.

That change increased sinkings about 75%; the Sept '43 fix to the Mk 6 only raised them about 20%.