United States participation in the minesweeping effort was overseen by Rear Admiral Strauss aboard the repair ship "Black Hawk", from which he had commanded the minelaying operation. Tugs and towed Admiralty wooden sailing smacks "Red Rose" and "Red Fern" out to conduct the first trial sweep in December. Sweeping was accomplished by suspending a serrated wire between two ships on a parallel course. While held underwater by planing devices called "kites", the wire would foul the cables suspending the buoyant mines above their anchors. If the serrated wire parted the mine mooring cable, the mine would bob to the surface to be destroyed by gunfire. The smacks swept and destroyed six mines before winter weather halted further work at sea. The winter was spent testing an electrical protective device to reduce the risk of sweeping the antenna mines with steel-hulled ships. "Patapsco" and "Patuxent" tested the protective device by sweeping 39 mines in March. Royal Navy minesweeping efforts involved 421 vessels manned by 600 officers and 15,000 men from 1 April to 30 November 1919.