ISIS went to school on how we were collecting intelligence on terrorist organizations by using telecommunications technologies. And when they learned that from the [Edward] Snowden disclosures, they were able to adapt to it and essentially go silent.

One great lesson from history we need to keep on re-learning. It is that sometimes your adversaries tell you exactly what they're going to do. How many times did [Osama] bin Laden say prior to 9/11 that he was coming after the U.S.? ISIS made clear that when they established their caliphate in Iraq and Syria, they were coming after the United States too.

The one thing that struck me right off the bat was what Donald Trump said about Benghazi.There is this view out there that [Hillary Clinton] lied about what caused the attack, that she said it was the video.

Companies made these decisions about encryption when they were finding it very difficult to sell their products overseas because the [Edward] Snowden disclosures created the impression that the U.S. government was inside this hardware and software produced by them. They needed to do something to deal with the perception.

I'm concerned, too, about ISIS' ability, right, to infiltrate people. But we have got some very effective, robust processes for vetting people. We brought in thousands of Iraqi refugees after the Iraq War. Not a single one has ever turned out to be a terrorist because the vetting was so good.

One of the lessons we've learned from the last 25 years of terrorism is that groups that have safe havens are able to develop external attack capabilities in a way that groups that don't have safe havens are not. So we need to find a way to squeeze them significantly in their safe haven. Taking away territory that really matters to them is really, really important because it prevents them from focusing on external attacks.

I want the vetting to be solid. But I also want to bring these people in because not bringing them in sends a message, right, to the Muslim world and plays into the ISIS narrative and the Al Qaeda narrative, right, that this is a war between religions. And we can't have that.