How did convoys protect merchant ships during naval wars?

The convoy system protected merchant ships by consolidating them into large, organized groups rather than allowing them to traverse the high seas as isolated, vulnerable targets. By grouping vessels together, it became logistically feasible and strategically efficient to assign armed escorts—such as destroyers and patrol vessels—to provide a protective screen or cordon around the merchant fleet.12

This defensive formation forced enemy submarines to risk entering the range of the escorts' weapons, including torpedoes and depth charges, if they wished to attack the merchant ships. During World War II, the system was further enhanced by the integration of sonar, air escorts, and improved radio communications, which allowed for better coordination against coordinated enemy tactics like "wolf packs".1

Ultimately, the convoy system proved highly effective; statistics from the Battle of the Atlantic show that the vast majority of ships lost to submarines were those sailing unescorted or as stragglers, rather than those within a protected convoy.1