It is true that there is a bewildering number of armed opposition groups in Syria - in 2013 a BBC "Guide to the Syrian rebels" estimated 1,000 such groups.

Among these those aspiring to create an Islamic State are said to be the most effective fighting force. Of course the term "Islamic State" can mean a range of things - Iran, Arabia and Isis would all claim that description, and deny it to the others. However a very sizeable number do have a close affinity with Isis or with Al Qaeda. The leading UN diplomat Stefan de Mistura offered to accompany such fighters out of Aleppo to Isis territory in a bid to end the bloodshed in Aleppo.