“The invasion of Iraq was supposed to turn the country into a democracy that posed no threat to the United States, or the rest of the world. Thirteen years later, Iraq has collapsed into three warring states. A third of the country is controlled by ISIS, who have also taken huge amounts of territory in Syria. VICE correspondent Ben Anderson gains exclusive access to the three front lines in Iraq, where Sunni, Shiite and Kurdish forces are fighting for their lives. Anderson visits with the Russian military forces in Syria, meets captured ISIS fighters in Kurdistan, and interviews US policymakers about how the situation in Iraq spun out of control.”
Many young students are especially baffled at how a terrorist organization can seize control of large chunks of territory. If you are looking for a good video introduction that explains how and why ISIS was able to gain power and than gain and maintain territory, this is it (it’s classroom safe despite the source).