PQ 18's protection was not limited to destroyers, anti-aircraft ships, and its escort carrier. Submarines trailed inside the convoy formation, ready to move outward if a German surface raider appeared. Their placement protected them from immediate contact while keeping a torpedo threat close to the merchant columns. The detail shows how an Arctic convoy could combine offensive and defensive layers against air, submarine, and surface attack.
Notable Point · 1:34:36-1:34:48
Why PQ 18 carried submarines inside its screen
Submarines waited within PQ 18's formation so they could sortie against a German surface force approaching the convoy.