I think Putin wants to recreate as much of the Soviet Union as he can through a variety of different means. He's invaded parts of Georgia, took Crimea, southeastern Ukraine, bases in other countries.

There are some ideas that will translate from Iraq to Afghanistan and there are many that will not. The first lesson of counterinsurgency, in fact, is that every situation is truly unique, has its own context, its own specific set of factors - and you have to understand that context in enormous detail to be able to craft a sound and comprehensive approach.

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

I am neither a pessimist nor an optimist. I am a realist, and the reality in Iraq is that it has been very hard and it continues to be hard.

This cannot be the United States being the air force for Shia militias, or a Shia on Sunni Arab fight.

The progress in Iraq is still fragile. And it could still be reversed. Iraq still faces innumerable challenges, and they will be evident during what will likely be a difficult process as the newly elected Council of Representatives selects the next prime minister, president, and speaker of the council.

I think no commander ever is going to come out and say, 'I'm confident that we can do this.