Syria's war has raged for well over a year in a region of intense US interest. The country shares borders with Iraq, Syria, Lebanon, Israel and NATO ally Turkey. President Bashar al-Assad's regime has a chemical weapons stockpile. The country is a close ally of Iran. And the US has long urged Syrians, under both Republican and Democratic administrations, to upend their country's political order and build a new order while successively piling sanctions on the central government.