When you enlisted into the armed forces you swore to support and defend a Constitution that did not yet fully apply to you. You chose to endure the same sacrifices as your fellow comrades in arms to preserve the freedom of a land that was not yet fully yours. You accepted that you might have to pay the ultimate price on behalf of a nation to which you did not fully belong. Now, you will officially become citizens of the United States, a country to which each of you has already borne true faith and allegiance in your hearts and your deeds.

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.

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.

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.

If you don't want to have to kill or capture every bad guy in the country, you have to reintegrate those who are willing to be reconciled and become part of the solution instead of a continued part of the problem. And then, above all, the resources.

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 did a week-long assessment in 2005 at (then Defense Secretary Donald) Rumsfeld's request. Following our return, I told him that Afghanistan was going to be the longest campaign of what we then termed "the long war."