When the Islamic State group took over Mosul in Iraq in 2014 they flooded the internet with pro-IS propaganda.
One historian living in the city decided to launch a counter-narrative online.
Omar Mohammed set up "Mosul Eye" to expose the atrocities and failings of IS fighters, but at great personal risk.
Omar tells Witness History how he posted news from Mosul to the outside world from right under the noses of the Islamic State group.
He says it was his duty to tell the real story.