"As the oil tanker began to emerge from another hard right turn, Matsumura ordered the tube's muzzle door opened, and waited. The I-21 slowly reached a ninety-degree angle to the target's path. The commander gave the order. 'Fire!'" Thus began one of the great unknown stories of World War II-an attack on a U.S. commercial vessel off the Central Coast of California in December 1941. That it happened was stunning enough. That so few even know it happened is all the more so. Now, the untold story.