The primary objective of the Market Time coastal patrol was to prevent the enemy from strengthening his forces in South Vietnam through seaborne infiltration of supplies and munitions. The North Vietnamese Naval Transportation Group 125 used steel-hulled, 100-ton trawlers and seagoing junks to infiltrate the South. The Viet Cong operated smaller junks, sampans, and other craft within South Vietnamese coastal waters, and limiting this movement also became a responsibility of the Market Time forces.
The coastal surveillance operation was organized around nine (initially eight) patrol sectors covering the 1,200-mile South Vietnamese coast from the 17th parallel to the Cambodian border and extending 40 miles out to sea. Within these areas, ships and craft of the U.S. Navy searched for contraband. American aircraft operating from ships offshore and from bases in South Vietnam, Thailand, and the Philippines flew search patterns over the Market Time area. By 1968 the patrol generally was divided into three zones: (1) an air surveillance sector farthest out to sea; (2) an outer surface barrier patrolled by large U.S. ships; and (3) an inner, or shallow-water, barrier patrolled by U.S. and South Vietnamese boats and craft and Coastal Force junks. Mobile units of Inshore Undersea Warfare Surveillance Group 1, Western Pacific Detachment, deployed to South Vietnam in April 1966 to form an additional screen.
