The convoy system in World War I involved organizing ships into large groups under the protection of armed naval vessels to provide better defense and countermeasures against German U-boat attacks. The ships protected were usually civilian merchant vessels, military supply ships and troop transports. Warships, such as destroyers, cruisers and torpedo boats, were used for convoy protection. They also sometimes deployed aerial reconnaissance to spot potential underwater U-boat movement.
German U-Boats were highly successful during the early years of World War I in disrupting the Allies' maritime supply lines. The armed submarines would emerge from under the sea, torpedo an unsuspecting vessel by surprise and then slink back under the surface without worry of retaliation. These tactics caused major damage to the Allies' war effort by targeting both combatant and neutral vessels. Losses for the Allies mounted to over 25 percent of shipping vessels.
The British admiralty was at first extremely reluctant to commit to convoy tactics, arguing that warships would be put to better use elsewhere. However, the successful use of convoys in protecting French coal shipments eventually convinced them otherwise. In less than a month, shipping losses dropped from over 25 percent to less than 1 percent thanks to convoy tactics.
Variations on the convoy system have been used by many nations in naval conflicts since the tactic's widespread use during World War II.