[RayChuang88]

Correct. US submarine forces during World War II effectively choked off Japan's supply of raw materials like minerals and oil, and that so degraded the Japanese military that if we had carried out Operation Downfall, the defense of the Japanese home islands would have not have lasted long other than a massive casualty toll among the Japanese defenders.

[ImJustAnotherOkie]

The Radar equipped B24’s helped a little bit.