The Entente powers began World War I without any formal anti-submarine countermeasures. However, the Entente developed countermeasures through trial and error over time. Success was moderate until America joined the war. with America came the arrival of subchasers to the Mediterranean Theater of Operations. This highly specialized vessel helped turn the tide against U-boats. a true counter to the U-boat threat in the Mediterranean did not come until October 2, 1918 with the bombardment of Durazzo. This thesis discusses the development of Entente anti-submarine capabilities and illustrate how America's contribution led to success. a detailed analysis of the rarely discussed bombardment of Durazzo is included using archival documents.