Under the cover of encryption, terror masterminds provide recruits with the tactics and tools necessary to carry out attacks using small arms and explosives. None of this requires any overseas travel.

Today, few terrorist organizations still employ the 'al-Qaeda model' in which individuals travel to terrorist training camps overseas and then are deployed to the West to inflict atrocities.

In our globalized world, our domestic prosperity depends heavily on the world economy, which, of course, requires stability and order. Who provides that stability and order? The U.S. military.

If we had maintained a small, residual force in Iraq, I don't think the Islamic State would have risen to power as it has.

We now have a better appreciation of the linkages in such terror attacks and a better assessment of how to articulate it in public.

I think that the public debate that we had on the Iran deal was very important. That's probably one of the most consequential things most of us will ever vote on ; a nuclear arms control agreement with a mortal enemy. And the White House - despite all their efforts - failed miserably.