US-backed forces breach IS defences in heart of Syria's Raqa

US-backed forces have penetrated the heavily fortified heart of jihadist bastion Raqa for the first time, in a key milestone in the war against the Islamic State group in Syria.Air strikes by the US-led coalition battling IS punched two holes in the medieval wall surrounding Raqa's Old City, allowing fighters of the Syrian Democratic Forces to breach the jihadists' defences, Washington and the SDF said on Tuesday.The advance -- the culmination of a nearly eight-month campaign -- comes as the jih