The region of Nagorno-Karabakh is considered to be one of the most heavily mined regions of the former Soviet Union. Mines were laid from 1991–1994 by both Azerbaijani and Armenian forces during the First Nagorno-Karabakh War. The United Nations and the United States had estimated the number of mines in Nagorno-Karabakh at 100,000, but after its 1998 assessment mission, the UN Mine Action Service concluded that the mine problem was not nearly as bad as original estimates portrayed.