Syrian refugees waiting on the Syrian side of the border crossing  near Akcakale, in Turkey’s Sanliurfa province, on Wednesday. Iran has denied it has deployed troops in Syria to bolster the Syrian army and its militia allies although this has been widely reported in the Syrian media. Photograph: Sedat Suna/EPA

UN special envoy Staffan de Mistura estimates that Iran spends $6 billion (€5.3 billion) a year to sustain the Syrian regime. This figure apparently e(...)