Iran's involvement in Syria carries growing costs

The killing of a commander in the Revolutionary Guards Corps at the hands of ISIS also highlights the extent of Iranian involvement in Syria and the dire straits in which Assad finds himself, Washington-based analysts say.

Brig. Gen. Hossein Hamedani was killed outside Aleppo, Syria, where he was advising the Syrian army in its fight against extremists, Iranian state media reported Friday.

Iranian media carried messages of condolence from Iranian President Hassan Rouhani, who described Hamedani's death as a big loss and applauded the senior commander for his bravery.

"He was in charge of [Iranian] operations inside Syria," said former CIA officer Reuel Marc Gerecht. "He'