South Sudan's President Salva Kiir and rebel leader Riek Machar signed a peace deal on Wednesday in the margins of a summit in Ethiopia. South Sudan plunged into a devastating war two years after its 2011 independence, when a political dispute between Kiir and Machar exploded into military confrontation. A previous 2015 peace deal fell apart after Machar forced out of Juba in a battle with government forces that killed tens of thousands.