Guerrilla warfare is fought by using the landscape to avoid open battle. Raids and surprise attacks are used. The Vietcong were used to the terrain and the climate. They used the Ho Chi Minh Trail to keep their forces supplied.
The Vietcong were supported by the South Vietnamese peasants because they would offer to help them with their daily work.
It was difficult for American troops to know who was a Vietcong and who was not.
The Vietcong had a system of tunnels stretching over 200 miles. There were hospitals, armouries, sleeping quarters, kitchens and wells underground. These tunnel systems could hide the Vietcong and helped them fight their guerrilla war.
The Vietcong and North Vietnam were supported by the Soviet Union (USSR) and China who supplied money and weapons.
The Vietcong captured 75 per cent of main towns in South Vietnam for a few hours, including the American Embassy in Saigon.
The Americans realised that they could not win a war against such a dedicated and widespread enemy.