Shia Muslim foreign fighters motivated by an increasingly politicised religious identity are coming to Syria to fight for President Bashar al-Assad in numbers that some observers argue match or even outnumber the Sunni militants who have joined the armed opposition.

While the estimates are contested, they show how much Syria’s war has become embedded in the fabric of Shia communities across the region – posing both advantages and risks to Mr. Assad and his main backer, Iran.

The number of independent Shia fighters in Syria is estimated to range between 8,000 to 10,000, mostly from Lebanon and Iraq, though anecdotal evidence suggests some come from as far as Azerbaijan and Afghanistan. The number of Sunni fighters is thought to be similar, with foreigners coming from around the world, but mostly from Arab countries.