Complex sentence: PAVN resistance was almost nonexistent and American casualties were light; with no previous allied presence around Khe Sanh, the North Vietnamese had seen no need to maintain large forces in the area.
Split into simpler sentences: PAVN resistance was almost nonexistent, and American casualties were light. With no previous allied presence around Khe Sanh, however, the North Vietnamese had seen no need to maintain large forces in the area.