According to a Sky News correspondent, Russian President Vladimir Putin's circle of allies is shrinking, having lost Bashar al-Assad, Nicolas Maduro, and now Ali Khamenei within a year.

Syria is confronting a significant security challenge as militias loyal to Bashar al-Assad launch new attacks in the west, while ISIS also initiates new offensives in the east.

It's been a little over a year since the fall of Bashar al-Assad in Syria ended a 14-year civil war. More than 1.3 million Syrians have returned home since then, according to the UN refugee agency, primarily from neighbouring countries such as Turkey, Lebanon, Jordan, Iraq and Egypt — but also from as far away as Canada.