Syria’s Assad Regime Fights to Survive Rebel Onslaught

President Bashar al-Assad’s political survival was under threat on Saturday as his government battled opposition rebellions around the country and one of his most important allies, Iran, pared back military support.

By Saturday morning, the main rebel offensive that began on Nov. 27 had reached the outskirts of the strategic city of Homs, only about 100 miles from the seat of Mr. al-Assad’s power in the capital, Damascus. But the opposition fighters were facing some of the stiffest resistance they have encountered so far from government forces there, who are trying to block the rapidly moving rebel advance heading toward Damascus.

Syrian government forces are still stationed on the outskirts of Homs and were shelling areas newly captured by the rebels, according to a British-based war monitoring group, the Syrian Observatory for Human Rights. There were also clashes between rebels and government forces north of the city, the Observatory said.

Still, it is unclear how long Mr. al-Assad can hold onto the rapidly shrinking pocket of territory under his control, especially without the help of one of his staunchest allies, Iran. The regime in Tehran has lent robust military support that was crucial to Mr. al-Assad’s survival over the past 13 years of civil war.

But late on Friday, Iran moved to start evacuating military commanders and other personnel from Syria, according to Iranian and regional officials.