Auxiliary Patrol
The Auxiliary Patrol was an antisubmarine initiative by the British to help combat German submarine operations in the early stages of World War I. It was the pioneer of anti-submarine warfare.
The majority of British trawlers were commandeered by the Admiralty, and those left were obliged to fish in groups of 20 with additional protection.
The Auxiliary Patrol was crewed by fishermen and led mainly by Merchant Navy men commissioned into the Royal Naval Reserve. They operated as trawlers do, in all weathers. Their trawlers were retrofitted with armaments, typically 3,6 or 12-pounder guns as well as 7.5" Bomb Throwers (Anti Submarine howitzers). Specialist crew such as signallers and gunners were also put on board.
Later in the war the Admiralty built 3 classes of larger trawlers as well as developing a new special class of Minesweeper.
By the Second World War, the Royal Navy had formed a specialist minesweeping capability, and the Royal Naval Patrol Service was formed, known to many as "Harry Tate's Navy".