Short for viet cong, these are the little yellow-hatted people you are fighting, they have random stats and attack from random side of the map, though sometimes they attack from all sides. They will try to defend themselves using the bunker, trench or sandbag positions on the screen. You are supposed to attack their positions and fight against their determined counter-attacks to take over the base they lost. They vary in skill and equipment, just like your men. However, the occasional one are masters of battle and they cap rip your forces to shreds. Their attacks contain random amount of men from only 8 to 30+ mass invasion. Later during the game, they start using artillery against you.
VC either used hit'n'run tactics or were trying to ambush some unlucky platoon. They were native North-Vietnamese, Cambodian or Laosian, some where from China or the Soviet Union. Their ally was NVA, North Vietnamese Army, what was mainly forces supplied by Soviet Union or China. They caused plenty of casualties for Unites States Armed Forces (58 267 KIA or non-combat deaths and MIA, 303 644 WIA), though approximately 1 100 000 men were killed from Viet Cong's and North Vietnamese Army's ranks. They were often killed in masses by US aerial supremacy, massive firepower and highly trained infantry. Their commanders were often trained by Soviet Union and managed to create extensive logistics network that US couldn't destroy. Their most succesful attack was called Tet Offensive where over 100 cities were attacked. Offensive failed, but its massive scale revealed Vietnam War to the public and started the end of United States campaign in Vietnam. It eventually was ended by VC and NVA attack to Saigon (capital of South Vietnam) where 450 000 fighters attacked against Saigon's 31 000 defenders out-numbering them 15 to 1.
In Urb's words: "They range from inexperienced recruits to skilled veterans."