The XXI was not the fastest sub during WWII!

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.

All they had to do is wait a few miles out from important target islands for the US fleet. This would have a heavy impact on Nimitz's and others campaign plans if not crippling it all together.

US ASW probably would have been ineffective as the subs would only be operation a few miles from their own home bases, well within their own ASW/patrol umbrella.

Nope. The realities of WW2 submarine warfare or why the U-Boat campaign failed while the American submarine war was a success indicate an entirely different conclusion.

They attempted exactly what you suggest and failed totally, losing more boats than targets sunk to radar equipped aircraft, radio location and submarine ambushes. Acting as mobile minefields in defence of every potential island target would have been a desperate strategy, doomed to failure as finite resources required for other vital missions would have necessary and have drawn off the defensive boats. Once the US CVBG's sat over the horizon, there was no more Japanese air cover and the boats would have died, tied to a location they could not possibly defend against an alert, superior ASW force.

The Japanese faced far more formidable problems than the U-Boats, the distances were vast, the air threat unbeatable and they had lost the technology war before firing a shot. Not even their uber-torpedoes could save the day.

[Kapt Z]

Originally Posted by Randomizer

Nope. The realities of WW2 submarine warfare or why the U-Boat campaign failed while the American submarine war was a success indicate an entirely different conclusion.

They attempted exactly what you suggest and failed totally, losing more boats than targets sunk to radar equipped aircraft, radio location and submarine ambushes. Acting as mobile minefields in defence of every potential island target would have been a desperate strategy, doomed to failure as finite resources required for other vital missions would have necessary and have drawn off the defensive boats. Once the US CVBG's sat over the horizon, there was no more Japanese air cover and the boats would have died, tied to a location they could not possibly defend against an alert, superior ASW force.

The Japanese faced far more formidable problems than the U-Boats, the distances were vast, the air threat unbeatable and they had lost the technology war before firing a shot. Not even their uber-torpedoes could save the day.

Agreed.

Sure a more aggressive IJN submarine campaign would have hurt the US effort and caused more losses, but like the kamikazes, it would not have changed the final outcome- crushing defeat.

Besides, as Yamamoto knew in 1941. There was no way that Japan could compete with the US once the American industrial base got rolling.

[Hitman]

Of course it wasn't the fastest ... look at my signature

http://en.wikipedia.org/wiki/German_Type_XVII_submarine