The brutal propaganda video released by Islamic State militants showing the murders of five people it claims worked for British intelligence services is the latest in a string of such films to be made since the group grabbed the world’s attention by taking Iraq’s second biggest city in 2014.

9 June 2014 Mosul falls to Islamic State fighters, with the then Iraqi prime minister Nouri al-Maliki declaring a state of emergency and pledging to arm civilians and reorganise the country’s ailing military forces. The city was the third to fall under the jihadis’ control after Falluja and Ramadi as it continued its rapid advance into Iraq.

29 June 2014 The militants claim the establishment of a new caliphate that incorporates parts of both Iraq and Syria. The group, which had called itself the Islamic State in Iraq and the Levant, shortens its name to Islamic State.

Early August 2014 US airstrikes on Islamic State targets begin after the group traps thousands of members of the minority Yazidi sect on a mountain in Iraq. It is believed they will be murdered by the militants if they come down from the mountain, while they face death by dehydration if they stay where they are.

Read the article “How ISIS Spread its Deadly Ideology — A Timeline” on theguardian.com.