Targeted By The U.S. - But Is The Khorasan Group In Syria Real?

With a coalition of 40 countries behind it, the U.S. began airstrikes in Syria. And U.S. officials revealed they've targeted a group that poses a "bigger threat" to the United States than ISIS: Khorasan. But despite the alleged threat, there's little evidence to suggest the group exists. AJ+ breaks down what we know about the Khorasan group.