The guerrilla tactics of the Vietcong were very effective for a number of reasons. The Vietcong was a highly organized operation with control centers hidden throughout South Vietnam that were rarely identified by American forces. It had integrated a complex system of supply and communication lines along what was known as the Ho Chi Minh Trail. In this way, China supplied the Vietcong with weapons for use against small groups of American troops. The ability of the Vietcong to blend into local populations made it extremely difficult for Americans to defeat them.
The difficulty in fighting the Vietcong was the covert nature of their operations. American soldiers could not know if they were engaging an enemy or a civilian. This element of surprise resulted in large scale American casualties. This also led to highly publicized atrocities on the part of American troops that shocked people in the states. These acts of atrocities, combined with the number of casualties quickly eroded public support for the war.
The Vietcong also used nontraditional tactics such as booby traps or hit-and-run type attacks. Guerrillas could execute a quick attack on small numbers of troops and quickly retreat back to underground tunnels located in the jungle. The Vietcong would also force civilians to attack American troops, sometimes utilizing children.
The Vietcong had an intricate network of tunnels that spanned for hundreds of miles throughout the jungle. American troops were not trained to deal with unconventional means of warfare and the end result was that these methods frightened and confused them.