The president and I sat down in the Oval Office, and he expressed very clearly that what he wants from me is my best professional military advice.

Don't forget Yemen, where there are also extremist elements, as we saw recently.

Afghanistan has other enormous challenges as well, including a political system that is still very much developing, although there has been some progress in the past several years.

Over the last few years they have done a superb job in their fight against al-Qaida. As you may recall, our embassy in Jedda (in Saudi Arabia) was overrun some four years ago and a number of foreign workers went home because of violence against them.

I just don't know whether it was all destroyed years ago - I mean, there's no question that there were chemical weapons years ago - whether they were destroyed right before the war, (or) whether they're still hidden.

Every civilian's death diminishes us, collectively.

ISIS is on its way to defeat but terrorism threat persists.