Hunter-killer Group

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Hunter-killer Groups, also called Convoy Support Groups, were teams of anti-submarine warships built to hunt and destroy submarines during World War II. They used advances in signals intelligence, cryptography, radar, and sonar to find and sink subs. These groups typically centered on an escort carrier that provided air reconnaissance and cover, with a flotilla of corvettes, destroyers, destroyer escorts, frigates, and sometimes Coast Guard cutters armed with depth charges and Hedgehog mortars.

The Royal Navy began with fleet carriers escorted by destroyers for this role. After the attack on Ark Royal by U-39 and the loss of Courageous to U-29, the Navy pulled fleet carriers from anti-submarine patrols. The idea in 1942 was to form groups that could reinforce a convoy’s escort. In early 1943, the Allied Atlantic Convoy Conference approved ten groups with an escort carrier each—five for the North Atlantic routes and five for the Middle Atlantic routes—so faster ships could become mobile reinforcement groups rather than just convoy screens.

In March 1943, some Western Approaches groups were reduced to form four new support groups, plus a fifth from Home Fleet destroyers. In April 1943, the 2nd Support Group (Black Swan-class sloops) began patrolling the Gibraltar routes, while the 1st and 3rd Groups (with other sloops, frigates, and destroyers) started responding to HX, SC, and ON convoys under attack. The first groups with escort carriers appeared later that month around HMS Archer and HMS Biter. The United States Navy formed its first group around USS Bogue, with Wickes and Clemson-class destroyers.

A typical group had about six ships, but damage and mechanical issues often limited operations to three or four ships. Slower group ships couldn’t always keep up with faster units that moved between groups. VLR patrol bombers sometimes supported groups without escort carriers. These early hunter-killer groups played a key role in the turning point known as Black May in 1943. As production of anti-submarine ships and escort carriers grew, more groups were created and the Allies could shift from protecting convoys to actively hunting submarines.

During the Cold War, the United States Navy built modernized hunter-killer groups in case Soviet submarines threatened North American shipping. As large anti-submarine aircraft became too big for escort carriers, Essex-class carriers were reclassified as anti-submarine warfare carriers (CVS). Some destroyers were renamed escort destroyers (DDE) and equipped with new ASW weapons like Hedgehog. The plan was for each CVS to be supported by eight DDEs—four to screen the carrier and four to attack submarines found by aircraft.

Vietnam War costs prevented replacing these ships when they aged. New mid-ocean ASW roles were filled by SOSUS and shore-based Lockheed P-3 Orion patrol aircraft, which took over the submarine-hunting work that hunter-killer groups had done at sea.