AP Photo

The killing last week of a senior Iranian Revolutionary Guards Corps commander near the Lebanon-Syria border has rekindled speculation about Iran’s activities in Syria, particularly its ties to the militia groups fighting alongside the Syrian government. With rebel forces having gained control of vast swaths of northern and eastern Syria in recent weeks, and the U.N. envoy Lakhdar Brahimi warning that Syria is being transformed into “a playground for competing regional forces and governments,” the precise nature of Iran’s role in the conflict is being held to more scrutiny than perhaps any moment since the conflict began 22 months ago.