The retaking of Aleppo marks the first major development in years in Syria's grinding civil war, which had largely fallen from the world's headlines. It also raises fresh questions about the opposing sides,

Syria's civil war has exploded back into life after Islamist rebels launched a lightning offensive on the northern city of Aleppo.

Diminished support for the Syrian government from Iran, Hezbollah and Russia enabled opposition forces to take the initiative and seize new territory.