British forces had seen signs of a submarine but lacked the organized detection and hunting systems later associated with anti-submarine warfare. U-21 watched Pathfinder's destroyers turn back, then fired a single torpedo as the cruiser retraced their route without zigzagging. Pathfinder's officers tried a hard turn by reversing one engine and driving the other ahead, but the warning came too late. An earlier sighting might have allowed an escape. Taking no evasive action could instead have moved the hit into the machinery spaces and prevented the magazine explosion, although flooding might still have sunk her. A slightly larger turbine-powered scout could also have carried meaningful torpedo protection. The loss combines a predictable tactical risk with chance in the torpedo's point of impact.
Notable Point · 24:02-27:41
A submarine threat the fleet was not ready to hunt
Pathfinder retraced a route without zigzagging while British forces still lacked an organized submarine-hunting system, leaving little margin once U-21 fired.