The Euphrates River is a simmering front line in the struggle for the new Syria. It separates the country’s two largest armed camps, marking the physical divide between clashing visions for the future. On one side is the army of the new Damascus government, dominated by Islamist factions who took down a dictatorship. On the other are the forces of a region run by Kurds, ready to guard their hard-won independence with their lives. With tensions rising, Reuters journalists travelled 1,800 kilometres across this divide in the summer, visited key strategic centres on both sides of the waterway and interviewed dozens of military and civilian officials, activists, and displaced people. They found a lawless frontier under the control of armed...