I've been in a position before where a president has turned to me in the Oval Office in a difficult moment, without any pleasantries, and said, 'I'm asking you as your president and Commander in Chief to take command of the international security force in Afghanistan.' The only response can be, 'Yes, Mr. President.'

The tragedy is that political leaders failed so badly at delivering what Iraqis clearly wanted - and for that, a great deal of responsibility lies with Prime Minister Maliki.

You cannot deal with an industrial-strength extremist problem just with force of arms. You have to have that political component as well.

The truth is that a number of us have been saying for quite some time that it was only a matter of time until someone went to a gun show, bought a military-like semi-automatic assault weapon with a large capacity magazine, and did enormous damage.

The foremost threat to Iraq's long-term stability and the broader regional equilibrium is not the Islamic State, it is Shiite militias, many backed by - and some guided by - Iran.

Iran has had a very harmful effect in a variety of ways in the region... fomenting unrest to a degree in Saudi Arabia, undoubtedly in Bahrain, and definitely in Yemen with Hamas, with Lebanese Hezbollah among other activities in locations.

Every civilian's death diminishes us, collectively.

We're here so that Afghanistan does not once again become a sanctuary for transnational extremists the way it was when al-Qaeda planned the 9/11 attacks in the Kandahar area, conducted the initial training for the attackers in training camps in Afghanistan before they moved on to Germany and then to U.S. flight schools.

Reconciliation is what takes place, of course, at higher levels. President Karzai has been very clear about the red lines for reconciliation, accept the constitution, lay down their weapons, cut their ties with al Qaeda and essentially become productive or at least participating members of society in that regard.

The bottom line is, you really have to commit to something if you're going to be successful in it.

Like a nuclear disaster, the fallout from the meltdown of Syria threatens to be with us for decades, and the longer it is permitted to continue, the more severe the damage will be.

Leading the coalition military effort during the surge in Iraq in 2007 and 2008 was the most important endeavor - and greatest challenge - of my 37 years in uniform.

A certain degree of intellectual humility is a good thing.

If you're asked, you've got to serve - put aside any reservations based on campaign rhetoric... and figure out what's best for the country.

The fact is that Iran doesn't want to see the Taliban come back any more than do most Afghan citizens.

This is actually true of the overall fight against al-Qaeda and trans-national extremists, that as you put pressure on them in one location, they'll seek safe haven sanctuaries in other areas. So you do have to continue to pursue them. But they have less capability.

I'm living the dream.

I don't comment directly on actions or statements of candidates.

As we used to say when I was privileged to be the commander there, Nineveh province has the most diverse human terrain in all of Iraq - Sunni Arab majority to be sure, but also Shia Arabs, numerous Kurdish communities, and they are broken out into several different political parties.

The bottom line is that Daesh's defeat requires not just hammering them on the battlefield but, simultaneously, revived political reconciliation with Sunnis.

At least from a national security standpoint, none of the problems the U.S. and U.K. face will become easier to solve if the U.K. is out of the E.U.; on the contrary, I fear that a 'Brexit' would only make our world even more dangerous and difficult to manage.

Iraq's Sunnis need to be brought back into the fold. They need to feel as though they have a stake in the success of Iraq rather than a stake in its failure.

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.

Ethno-sectarian violence is a particular concern in Iraq, as it is a cancer that continues to spread if left unchecked.