Hunter-killer Groups, also known as Convoy Support Groups, were groups of anti-submarine warships that were actively deployed to attack submarines during World War II. The advances in signals intelligence such as High-frequency direction finding, in cryptological intelligence such as Ultra, and in detection technologies such as radar and sonar/ASDIC enabled the Allied navies to form flotillas designed actively to hunt down submarines and sink them. Similar groups also existed during the Cold War. A hunter-killer group would typically be formed around an escort carrier to provide aerial reconnaissance and air cover, with a number of corvettes, destroyers, destroyer escorts, frigates, and/or United States Coast Guard Cutters armed with depth charges and Hedgehog anti-submarine mortars.