Moscow insists warplanes from its aircraft carrier stationed off the Syrian coast did not target Aleppo, but Russia's intensifying intervention could be a game-changer in the momentum in this brutal war. Aleppo was Syria's economic hub with a pre-war population of two million. One million now live in the west of the city, in comparative safety. Those trapped in the east live in appalling conditions as over the past year more troops and considerable firepower, including advanced missile systems, have been moved by Russia onto the battlefield. There is no single group in charge: the area is divided between mainstream rebels backed by the USA and its allies, the al-Qaeda-linked jihadist group Jabhat Fateh al-Sham (formerly known as al-Nusra Front), and Kurdish forces, who say they support neither the government nor the opposition.