During the Vietnam War the border was crossed by Viet Cong supply lines, most notably the southern stretch of the Ho Chi Minh Trail, causing it to be heavily bombed by American forces. In return for tolerating the Viet Cong presence along the border, Cambodia attempted to extract territorial concessions, though with little success. In 1975 the nationalist-Communist Khmer Rouge took over Cambodia and made gaining some or all of Kampuchea Krom a priority. A brief Khmer invasion occurring the day after Saigon fell to North Vietnam was repulsed, and border discussions then took place from 1976 to 1977. With relations deteriorating numerous skirmishes occurred along the border, with Vietnam eventually invading Cambodia in 1978 and ousting the Khmer Rouge. Discussions on the border thereafter reconvened in 1983, with both sides in 1985 pledging to recognise the border as it was at independence. Discussions continued into the early 1990s. A treaty was signed in 2005, followed by on-the-ground demarcation, which was completed in 2012.