Just a week ago, al-Qaeda-linked rebels in Syria enjoyed an arc of dominance across the country’s north and east, ruling with brutality. But a series of stunning reversals in recent days has made clear that the militant group may be more vulnerable than it seemed, in part because its frequent kidnappings and attacks on fellow rebels have won it few allies. By Tuesday, the group, the Islamic State of Iraq and Syria, appeared increasingly desperate, with its fighters pushed out of some towns and turning to suicide bombings in a bid to hold on to pockets of Raqqah, the large north-central city that was its stronghold. Still, the group showed no sign of giving up easily, calling Tuesday for its followers to behead anyone associated with the Western-backed Syrian Opposition Coalition, which it accused of starting the conflict. For now, at least, a coalition of more-moderate Syrian […]