ISTANBUL — A still-murky deal last month that allowed a convoy of besieged Islamic State fighters and their families to travel across Syria to safety along the eastern border with Iraq continues to reverberate across the region, provoking outrage as well as a strategic rethink by the pro-U.S. government in Baghdad.The delicate diplomacy and volley of recriminations sparked by the unusual pact — which included a gruesome exchange as Islamic State fighters handed over bodies of Shiite soldiers from Iran, Lebanon and Syria — exposed escalating tensions between the capitals along the Shiite Crescent extending from Tehran to Beirut and opened a window to the complexities to come as Islamic State’s once-powerful “caliphate” faces imminent defeat on the battlefield.
