IS, al-Qaeda, and How Jihad Uses Chemical Weapons by Frank Gardner, BBC
There is a history of modern jihadists experimenting with and sometimes using chemical weapons, dating back to al-Qaeda's training camps in Afghanistan in the 1990s.
There is also a clear link between those experiments at the time and the IS leadership's strategy against its enemies today.
"The thing that surprised me is that they haven't used it (mustard gas) earlier," says Aimen Deen, a former al-Qaeda operative who witnessed chemical experiments first-hand.
"The experiments date back to 1997 in Afghanistan. They experimented with many different varieties of chemical weapons."
He says the gasses tested were homemade and included phosgene, chlorine and hydrogen cyanide. Rabbits and dogs were the most common animals to be used…