“Territory is arguably both ISIS’s greatest strength and its greatest weakness. The land the group seized in Syria and Iraq, which at its peak was thought to be as large as the kingdom of Jordan, enabled the Islamic State to aspire to its grandiose name by declaring a caliphate, drawing recruits from around the globe, and distinguishing itself from the world’s stateless terrorist and insurgent groups.”
Source: The Battle for Mosul: What’s the Islamic State Without a State? – The Atlantic