Significant use of landmines in Cambodia began with the Vietnamese occupation of the country - late 1970's until 1989. The landmines were laid by the Khmer Rouge, the Vietnamese and other factions - during various stages of conflict. The heaviest concentrations of landmines were at the border between Cambodia and Thailand. Since 1979, Cambodia has had over 64,000 landmine casualties (over 40,000 amputees) - the highest ratio per capita in the world. An estimated 4 to 6 million landmines and other unexploded ordinance were laid in Cambodia.