The Viet Cong were the military arm of the National Liberation Front that opposed South Vietnamese and US forces during the Vietnam War. Formed in 1960 with the goal of overthrowing the South Vietnamese government and reunifying Vietnam under communist rule, the Viet Cong used guerrilla warfare tactics like ambushes and hit-and-run attacks. They were able to defeat American forces through their familiarity with jungle warfare, extensive tunnel systems, and motivation to fight for Vietnamese independence against foreign influence.