"Terrorist groups like Daesh love a power vacuum, and so there is a risk that Daesh can exploit the chaos of a post-Assad Syria to resurface to an even greater extent," said Raphael Cohen, a senior political scientist at the RAND Corporation. Bashar Assad's overthrow has cleared the way for US strikes against the Daesh group in areas previously shielded by Syrian and Russian air defenses -- but the terrorists may also try to exploit the vacuum left by his fall.