How common was civilian killings? First of all, It’s a very grey area. The type of massacres you think of when you think of Nam were not all that common, but did happen. Usually by Korean / South Vietnamese / Nungs than Americans as part of the dirty laundry aka CIA Phoenix Program (which funded terror operations similar to the VC tactics) . Sometimes American units did the same, either as an indirect order of the Agency or Gung ho higher ups who didn’t give a hoot. Sometimes men went plain crazy, or blood thirsty. One VC tactic was to go into villages that were known sympathisers, take the village leader, take his wife, abuse her in front of village. Followed by their deaths. This was a method they used: pure fear. It worked well on the average villager. Who would speak out against such brutality when you have family to think of? The CIA had men go and do similar things to blame it on VC units to stir up feelings and create unrest especially in border countries. They played very very dirty. It was highly classified. An hypothetical scenario. Imagine a woman is coming toward you; suddenly you sense something off. Not far behind her is a little boy. He has something in his hands. It takes just one glimpse to see if it’s a grenade. Now the grey area begins.