Leader (AM-490) was laid down by J. M. Martinac Shipbuilding Corp., Tacoma, Washington, 22 September 1953; launched 15 September 1954; sponsored by Mrs. Norman Wordlund; reclassified MSO-490 7 February 1955, and commissioned 16 November 1955, Lt. Comdr. Harvey E. Toponce in command. This MSO class of minesweeper was constructed of non-magnetic materials, including a wooden hull and aluminum engines, and had a degaussing system to reduce the magnetic field of the vessel, so that it could move over magnetic mines without detonating them. It was equipped with a "magnetic tail", two thick cables spooled on a large reel aft of the superstructure. The power-generation system could send current through this split tail after it was streamed behind the ship, creating a magnetic field designed to set off magnetic mines after the ship passed over them. It carried conventional mine-sweeping gear as well.
Cambodia and Vietnam Operations
From 1959 through 1968 Leader alternated six WestPac cruises with U.S. West Coast mine warfare and mine countermeasure exercises. During her 1961 cruise. Leader became the first warship ever to visit the Cambodian capital of Phnom Penh when she completed the 180-mile transit up the Mekong River on 27 August, under the command of Lt. Commander Frank Kauzlarich. On this same cruise she directed South Vietnamese units in minesweep training operations. During her tour with the U.S. 7th Fleet in 1965, Leader again operated off South Vietnam, this time under more serious circumstances. From June to August she performed special minesweeping operations and played a major role in the expanded American effort to assist the courageous people of Vietnam in their fight against Communist aggressors. Her tour completed, Leader returned to Long Beach 14 December to resume training operations.
Market Time Operations
1966 saw an extensive overhaul for the minesweeper, from 9 May to 30 September. After further training and readying for deployment, Leader once again sailed for WestPac 6 January 1967. She participated in Market Time operations for the better part of her tour, returning to Long Beach 18 November. She operated locally through the first half of 1968. Then, on 12 August, Leader departed Long Beach for another extensive deployment, and continued operating off Vietnam into 1969.