Seven submarines and the West Coast threat

Seven Japanese submarines patrolled the American West Coast, probably sinking two merchant ships, damaging others, and fighting several encounters with the US Navy. Compared with the Battle of the Atlantic, Mediterranean operations, and the later American submarine offensive against Japan, this was a very small deployment. Seven boats could complicate coastal defense and shipping, but they could not cover the entire coast or impose comparable material losses. Their stronger weapon was fear, because a thinly spread force could make the threat appear much larger than it was. The order for I-17 to shell California while President Roosevelt was due to speak turned that imbalance into a deliberate psychological operation.