Aided by bountiful signals intelligence, Operation Teardrop succeeded in knocking out four of the seven submarines in Seewolf, and one of the three vessels sent as reinforcements. The U-Boats were intercepted both on the surface and submerged, reflecting the refinements in technology and tactics the U.S. Navy had implemented after the costly early years of the Battle of the Atlantic.

The U.S. Navy responded with overwhelming force against a potential threat to the continental United States—but proved too willing to bend its principles on the treatment of prisoners of war, escalating the use of torture when the prisoners did not confirm the interrogator’s incorrect assumptions, as often happens.

Ironically, it would actually be two U.S. submarines that first tested submarine-launched cruise missiles two years later. The weapon: an American copy of the V-1 buzz bomb.

Sébastien Roblin holds a Master’s Degree in Conflict Resolution from Georgetown University and served as a university instructor for the Peace Corps in China. He has also worked in education, editing, and refugee resettlement in France and the United States. He currently writes on security and military history for War Is Boring.

This article was originally published in 2016.