The first tank-to-tank engagement occurred in mid-1968 when a US reconnaissance airplane observed a PT-76 being washed by its crew in the Bến Hải River in the DMZ (17th Parallel). The Forward Air Control pilot radioed the tank's position to a nearby M48 Patton tank unit of the US 3rd Marine Tank Battalion. With the FAC adjusting fire, the Patton fired three 90 mm rounds; obtaining a hit with the third round. The tank crew abandoned their vehicle. Shortly afterwards, some returning F-4 Phantom jet fighter bombers, with ordnance to expend, observed the PT-76 and bombed the remainder of the vehicle.