Communist forces began digging a network of tunnels under the jungle terrain of South Vietnam in the late 1940s, during their war of independence from French colonial authority. Tunnels were often dug by hand, only a short distance at a time. As the United States increasingly escalated its military presence in Vietnam in support of a non-Communist regime in South Vietnam beginning in the early 1960s, North Vietnamese and Viet Cong troops (as Communist supporters in South Vietnam were known) gradually expanded the tunnels. At its peak during the Vietnam War, the network of tunnels in the Cu Chi district linked VC support bases over a distance of some 250 kilometers, from the outskirts of Saigon all the way to the Cambodian border.