Why Can't We Beat ISIS?

Every week, it's a new story of destruction and hubris from the self-proclaimed Islamic State, or ISIS. This week in Syria, the extremists emptied 30 villages and captured 300 Assyrain Christians. In Iraq, they smashed priceless artifacts that date back thousands of years.

But for all of the destruction, the ISIS force is relatively small. The U.S. estimates it is between 25,000 and 30,000. The U.S. military is the most powerful in the world. So, why is it so hard to defeat ISIS?

"The short answer is that we’re playing catch up," military strategist David Kilcullen told Here & Now's Robin Young. "We allowed ISIS to build up without significant opposition. We waited until it broke out and made a very significant expansion of territory last summer, and now we’re trying to catch up to something that’s been growing for years."