Armenia and Azerbaijan have faced each other off in a conflict over Nagorno-Karabakh for more than three decades. Border clashes between Armenia and Azerbaijan have killed about 100 troops on both sides in the largest outbreak of fighting between the longtime adversaries in nearly two years, fueling fears of even bigger hostilities. The mountainous region is part of Azerbaijan, but has been under the control of ethnic Armenian forces backed by Armenia since a separatist war there ended in 1994. Why are negotiations “failing” in border disputes nowadays?

