The Syrian regime of President Bashar al-Assad has suffered its biggest defection yet. Brigadier Manaf Tlas, a senior commander of the elite Republican Guard and a one-time close confidante of Assad, has joined the opposition sixteen months after an uprising in the country has claimed at least 15,000 lives.

A Syrian news agency confirmed that Tlas escaped to Turkey, making him the fifteenth brigadier to have joined the rebels. He is from one of Syria’s most illustrious and famous families.

Tlas’ father, General Mustafa Tlas, was Syria’s long-time defense minster and helped Assad consolidate his power when he took over from his father in 2000.