Iran began to evacuate its military commanders and personnel from Syria on Friday, according to regional officials and three Iranian officials, in a sign of Iran’s inability to help keep President Bashar al-Assad in power as he faces a resurgent rebel offensive.

Among those evacuated to neighboring Iraq and Lebanon were top commanders of Iran’s powerful Quds Forces, the external branch of the Revolutionary Guards Corps, the officials said.

Guards personnel, some Iranian diplomatic staff, their families, and Iranian civilians were also being evacuated, according to the Iranian officials, two of them members of the Guards, and regional officials. Iranians began to leave Syria on Friday morning, the officials said, speaking on condition of anonymity to discuss a sensitive issue.

Evacuations were ordered at the Iranian Embassy in Damascus, and at bases of the Revolutionary Guards, the Iranian and regional officials said. At least some of the embassy staff has departed.

Part of the evacuation is being carried out by planes to Tehran, while others are leaving via land routes to Lebanon, Iraq and the Syrian port of Latakia, the officials said.

“Iran is starting to evacuate its forces and military personnel because we cannot fight as an advisory and support force if Syria’s army itself does not want to fight,” Mehdi Rahmati, a prominent Iranian analyst who advises officials on regional strategy, said in a telephone interview.