But now, a U.S. military leader says he's worried about what could happen next if Iraqi troops manage to defeat ISIS altogether.

　　For some insight, we are joined now from Washington, D.C. by Douglas Ollivant, former National Security Council director for Iraq during the presidencies of George W. Bush and Barack Obama. He is a senior national security fellow at the New America Foundation and a partner at Mantid International.

　　So, first, why the pause in fighting?

　　DOUG OLLIVANT, MANTID INTERNATIONAL: Well, we're not sure. That's a single-source report. We're not confident that is what's happening, although, you know, knowing what's going on in the fog of battle is often difficult.

　　What we do know is that the battle has been going fairly successfully. It's possible they've taken a pause to call for more reinforcements. But in general, they've been — they've been pushing through the city of Tikrit, and we do expect them to control it in days to, you know, a week or 10 days at the outside.

　　HARI SREENIVASAN: You know, I referenced a comment, and it was from Army General Martin Dempsey. He said this week that any fight against ISIS is a positive thing, but he worried, quote, "what happens after the drums stop beating and ISIL is defeated, and whether the government of Iraq will remain on a path to provide an inclusive government for all of the various groups within it."

　　DOUG OLLIVANT: That's a legitimate concern. The good news today is that the initial indications are good. We have a front page story in "The Wall Street Journal" today about the Sunni residents around Tikrit being overjoyed at being liberated by the Shia militias. In fact, we have a report from "AFP" that states some of the Shia militias are setting up Sunni groups within them, that they are recruiting Sunni auxiliaries to their militias.

　　So, there are some initial good signs. Now, of course, in the longer term, the political reconciliation, the reconstruction of Tikrit, getting the services back up, their — you know, the economy moving again– these are all really important things that it's too early to tell if those are going to be as successful.

　　HARI SREENIVASAN: And there's also some concern, it seems, on the involvement of Iran in this fight. There was a report that an Iranian revolutionary guard commander was seen on the battlefield or leading some of the troops in Tikrit, and there was some response, also, from the Saudi foreign ministers saying, you know, what? This is proof that Iran is essentially taking over Iraq. I mean, is it very easy to get people off the battlefield and say, "Thanks for the help, back to your country now"?

　　DOUG OLLIVANT: Certainly, Iran is banking some very serious political capital with the Iraqis in their instantaneous and overwhelming support in their fight against the Islamic State. So, you know, Iran, in effect, has paid its dues and will probably enjoy some political support in the coming years because of that. That's something that the United States is just going to have to keep competing with Iran for influence in Iraq. It would be easy to just walk away, but instead, we need to stay in and really try to recover from some mistakes, I think, that were made early on that have given the Iranians some positional advantage in the aftermath of what will happen.

　　HARI SREENIVASAN: Is that what's leading to some of the tension in D.C. right now?

　　DOUG OLLIVANT: I think that's a big piece of it. I mean, there are, obviously, all types of things going on with Iran. This is just one piece of it.

　　The nuclear negotiations are in the air. The competition with Saudi Arabia is the in air. There's a huge propaganda battle that's going on, on the airwaves, in social media, you know, for the attention of the people, you know, lots of accusations that Iranian-backed groups are doing this. You know, they, of course, are pushing back saying that's just not the case.

　　So, yes, there are concerns, some of them legitimate, some of them less so, and we're going to see how this works out in the longer term. But there doesn't seem to be any alternative to let any Iranians help. We certainly don't want to tell the Iraqis, you know, kick them out of country and fight the Islamic State without this aid. That's not going to fly, either.

　　HARI SREENIVASAN: All right. Doug Ollivant joining us from Washington, D.C., thanks so much.

　　DOUG OLLIVANT: Always a pleasure.