How did the Viet Cong avoid detection during the cold war era?

The Viet Cong had nothing to do with the cold war. The cold war was between western nations and the communist eastern block. Vietnam is in Southeast Asia and the first nation into the county was France. In the late 1950's president Eisenhower promised support to the Vietnamese when the French pulled out. He made the agreement, JFK added advisors and troops, LBJ escalated it by sending more boots on the ground and drafted men. Nixon bombed Laos in secret, but eventually in 1974 ended our involvement.