Britain Introduces Convoy System

After April 1917's catastrophic shipping losses (860,000 tons sunk), Britain introduced the convoy system for merchant ships despite Admiralty resistance. The first experimental convoy sailed on May 10, 1917. Monthly losses fell dramatically: from 860,000 tons in April to 289,000 by November 1917. The convoy system, combined with improved depth charges and ASDIC sonar development, gradually won the Battle of the Atlantic. Germany's gamble that unrestricted submarine warfare would win the war before US intervention had failed.