It in the military, especially in the field (front lines), an officer might point to a map and state, "...intell says there's a large buildup of NVA...here...", then possibly …further adding, "...intell believes they might be elements of the B/5 infantry regiment...we'll insert here and sweep up to here...until contact is made...be prepared for...etc.".
A buildup of NVA=large amount of (ENEMY) North Vietnamese Army troops in a designated area..
We liked to know who we were fighting; NVA or VC. If it was VC, we knew it would most likely be a short fight, with the possibility of low to no casualties. If it was NVA, we knew it could be a serious battle, with lots of casualties..
It was not past the NVA to throw in some heavy stuff during a fight. If it was just VC, we pretty well knew it would all be small arms and grenades. (MORE)