Established in March 1965, the U.S.-South Vietnamese coastal patrols tasked with ending North Vietnamese infiltration of the South by water were collectively known as Operation Market Time. Close to shore their primary vessel was the Fast Patrol Craft (PCF), or "Swift" boat. Capable of 23 knots, armed with .50-caliber machine guns and 81-millimeter mortars, the crews of these boats often performed routine inspections of papers and cargo of civilian vessels.