 As PAVN activity continued to increase in the eastern DMZ, particularly north of Con Thien, the Marines decided to act.In addition to sightings of enemy tanks, Marine fighter pilots and aerial observers reported spotting trucks, truck parks, camouflaged revetments, storage bunkers, and trenchlines.Of special interest were repeated sightings of low, slow moving lights during hours of darkness which, it was assumed, came from enemy helicopters thought to be resupplying forward positions with high priority cargo such as ammunition and medical supplies or conducting medevacs.