After the collapse of the Soviet Union, border negotiations left substantial Uzbek populations stranded outside of Uzbekistan. In south-western Kyrgyzstan, a conflict over land between Kyrgyz and Uzbeks exploded in 1990 into large-scale ethnic violence; the violence reoccurring in 2010. By establishing political units on a mono-ethnic basis in a region where various peoples have historically lived side by side, the Soviet process of national delimitation sowed the seeds of today's inter-ethnic tensions.