After months of Syria bloodshed, stalled humanitarian aid deliveries and stop-and-start diplomacy, U.N. Syria envoy Staffan de Mistura is reconvening talks between government and opposition delegations on Thursday, in the latest bid to end the country's catastrophic six-year war that has killed hundreds of thousands of people and displaced millions more. Battlefield gains by President Bashar Assad's forces against Western-backed rebels, a new diplomatic push led by Turkey and Russia, and uncertainty about the Trump administration's strategy on Syria — the U.S.