ISIL gained prominence, when in early 2014 it drove Iraqi government forces out of key cities in its Western Iraq offensive,[42] followed by the capture of Mosul
[43] and the Sinjar massacre,



[44] almost causing a collapse of the Iraqi government and prompting a renewal of US military action in Iraq. In Syria, the group has conducted ground attacks on both government forces and rebel factions. The number of fighters the group commands in Iraq and Syria, was estimated by the CIA at 31,000, with foreign fighters accounting for around two thirds,[45] while ISIL leaders claim 40,000 fighters, with the majority being Iraqi and Syrian nationals.[25]

Adept at social media, ISIL became notorious for its videos of beheadings[46] of both soldiers and civilians, including journalists and aid workers, and for the destruction of cultural heritage sites.[47] The United Nations holds ISIL responsible for human rights abuses and war crimes, and Amnesty International has charged the group with ethnic cleansing on a "historic scale" in northern Iraq.[48] Around the world