In the summer of 2014, three years after America's full troop withdrawal from the Iraq War, President Barack Obama authorized a small task force to push back into Baghdad. Their mission: Protect the Iraqi capital and U.S. embassy from a rapidly emerging terrorist threat.

A plague of brutality, that would come to be known as ISIS, had created a foothold in northwest Iraq and northeast Syria. It had declared itself a Caliphate-an independent nation-state administered by an extreme and cruel form of Islamic law-and was spreading like a newly evolved virus. Soon, a massive and devastating U.S. military response had unfolded.