Understanding Syrian Unrest Starts With 3 Letters: HTS

Syria's long-running civil war has been off the radar for a while, but the stunning, out-of-the-blue capture of Aleppo—the nation's largest city—by rebels has changed that in a hurry. Those catching up with events will have to get familiar with a new acronym, HTS, short for Hayat Tahrir al-Sham, explains NPR. HTS is seen as the main rebel group behind the new military surge. Coverage:

• HTS shift: The group has ditched its original ties with al-Qaeda and has generally become more moderate in recent years under leader Abu Mohammed al-Golani, who has disavowed international terrorism and promised to embrace religious tolerance, per the AP.
• More independent: HTS operates out of western Syria. It "has been able to build that empire by primarily controlling most of the economic sectors in Idlib," Natasha Hall of the Center for Strategic and International Studies tells CNN. "They are more of an independent force than many groups."
• US view: The State Department made clear on Monday that it doesn't support HTS "in any way, shape, or form" and still considers it a terrorist organization, said spokesman Matt Miller, per NBC News. At the same time, Syrian leader Bashar Assad "is a brutal dictator with blood on his hands, the blood of innocent civilians," said Miller.

• Others in the mix: The war involves a complex mix of groups, and Al Jazeera has a primer. Also fighting against Assad are the Syrian Democratic Forces (SDF)—made up of US-backed Kurdish groups in the east—and the Syrian National Army (SNA), made up of Turkish or Turkish-aligned forces in the north. Assad's National Defense Forces, meanwhile, are backed by Russia and Iran.
• The battle: Insurgents led by HTS captured four new towns on Tuesday and are advancing to the fourth-largest city of Hama in central Syria, reports the AP. Meanwhile, the SDF says it captured seven villages in the east. However, Russian airstrikes helped Syrian troops recover some of the territory it lost last week. The civil war began in 2011 after Assad put down an uprising against his regime.

(More Syria stories.)