Thousands of foreign fighters have gone to Iraq and Syria, where civil war is raging. Many have Twitter and Instagram accounts which they use to document a personal view of life on the ground as a jihadi.
Many of these fighters are believed to have travelled from the UK, with others coming from European countries. The location of the following people cannot be confirmed definitely, but all claim to be in Iraq or Syria.
Some 9.3 million people in Syria are in need of humanitarian assistance; more than 2.8 million have fled to the neighboring countries.
This one was posted to Instagram with the hashtag #CatsOfJihad.
Any weapon will do, apparently.
Not everyone is a fan of the cats, however.
This Mitsubishi pick-up truck, fitted with a machine gun, has British number plates. It was registered in Birmingham.
BuzzFeed checked with the DVLA, and vehicle's MOT expired last October. It is pictured in an unknown location.
Guns get waved around quite casually.
There are also reports that American equipment seized from retreating Iraqi forces is being used by ISIS fighters.