South Sudan rivals have signed a ceasefire agreement after five weeks of violence that killed thousands of people and displaced more than half a million. Earlier efforts reached an impasse over key disagreements, including the rebels’ demand for the release of prisoners and the withdrawal of Ugandan troops fighting alongside government forces. The ceasefire is being hailed as the first step to ending the conflict, but both sides have voiced caution and reiterated concerns over unmet demands. The most recent bout of fighting began last month as a political dispute between President Salva Kiir and his former vice president, but quickly escalated into ethnic clashes that raised fears of a civil war.