I-400 Series Super-submarine

Lieutenant Commander Stephen L. Johnson had a problem on his hands; a very large problem. His Balao-class submarine, the Segundo, had just picked up a large radar contact on the surface about 100 miles off Honshu, one of Japan’s home islands, heading south toward Tokyo.  World War II in the Pacific had just ended, and the ensuing cease fire was in its 14th day. The official peace documents would not be signed for several more days.

As Johnson closed on the other vessel, he realized it was a gigantic submarine, so large in fact that it first looked like a surface ship in the darkness. The Americans had nothing that size, so he realized that it had to be a Japanese submarine.

This was the first command for the lanky 29-year-old commander. He and his crew faced the largest and perhaps the most advanced submarine…