Dutch peacekeepers sit at their military base in Gao, Mali, August 11, 2015. The United Nations has deployed 10,000 peacekeepers and poured more than $1 billion into Mali but its efforts to end a three-year conflict are threatened by the reemergence of a centuries-old rivalry between Tuareg clans. Picture taken August 11. To match Insight MALI-VIOLENCE/MILITIA REUTERS/Emma Farge