From: Dictionary of American Naval Fighting Ships

A person or group that originates or helps open up a new line of thought or activity or a new method or technical development.

(AM-105: dp. 1,250 (f.) 1. 220'6"; b. 32; dr. 10'9"; s. 18 k.; cpl. 105; a. 1 3", 2 40mm.; cl. Auk)

Pioneer (AM-105) was laid down 30 October 1941 by Pennsylvania Shipyards, Inc., Beaumont, Tex.; launched 26 July 1942; sponsored by Mrs. H. R. Jessup; and commissioned 27 February 1943, Lt. Comdr. H. B. Stevens in command.

Pioneer trained her crew and experimented with newly developed gear in the Gull of Mexico, Chesapeake Bay, and the Potomac before joining a Mediterranean-bound convoy at New York 14 May 1943, for the first of four escort voyages from New York or Norfolk to North African ports. In November she took up patrol and escort duty within the Mediterranean.

On 26 November, while bound east from Oran, Pioneer's convoy was attacked by enemy bombers. They hit merchantman Rohna and set her afire; Pioneer stood by, continuing to fire on the attacking aircraft while conducting the rescue of 606 soldiers and crewmen from Rohna. She protected critically important Allied convoys in the Mediterranean until assigned to the assault force for the Anzio operation early in January 1944. After training at Salerno, her group sortied from Naples 21 January to sweep a mile-wide channel into the fire support and transport areas, and then swept these areas themselves. When the transports entered the newly cleared area, Pioneer began antisubmarine and antiaircraft patrol, and then resumed escort duties' bringing reinforcements to Anzio 24 January.

Desperate German resistance by land and air as well as from the sea prevented & breakout from Anzio. Pioneer guarded the beleaguered beachhead, patrolling to seaward escorting supply and reinforcement movements, and sweeping mines dropped by enemy planes intent on isolating the beachhead by sea as it was by land. She returned to wider-ranging escort assignments when advancing Allied land forces broke through to Anzio late in May.

On 12 August Pioneer sortied for the invasion of Southern France. Again doughty little minesweepers led the way, clearing the assault area ignoring shore battery attacks while completing their complex and vital task. Patrol and sweeping operations included extensive activity to prepare newly captured Marseilles to receive shipping.

Pioneer sailed from Bizerte 24 November for stateside overhaul preparatory to Pacific deployment, for which she left Norfolk 15 February 1945 bound for Panama enroute to Hawaii. Arriving Pearl Harbor 18 March after underway training, Pioneer installed new radar gear and joined in exercises before getting underway for Okinawa 23 May. Calls enroute delayed her arrival until 7 August. For the remainder of the year, Pioneer joined in the gigantic task of clearing Japanese and Chinese waters of the thousands of mines laid in a decade of warfare. Peaceful use of the oceans restored Pioneer returned to San Pedro, Calif. 14 February 1946 to inactivate. She decommissioned and went into reserve at San Diego 8 July 1946. She was redesignated MSF-105 on 7 February 1955, and remains in reserve at San Diego into 1970. [Transcriber's Note: Stricken 1 July 1972, Pioneer was soon after sold to the Mexican Navy as where she served as Leandro Valle.]

Pioneer received 4 battle stars for World War II service.