RENEE MONTAGNE, HOST:

The assault on Mosul is moving faster than expected. Iraqi forces, with U.S. support, are now on the outskirts of the city. Mosul has been under the control of ISIS for more than two years with a million, perhaps more, people still living there. We've got NPR's Alice Fordham on the line. She is covering the offensive in northern Iraq.

And Alice, what is the latest?

ALICE FORDHAM, BYLINE: Well, so elite counterterror forces are now on the eastern edge of the city. There are slightly different definitions of where the city begins, which area is a village outside and which is a neighborhood of the city. But either way, they're either there or they will be once they have advanced a few hundred more meters. And they are moving pretty fast.

Now, it's important to note that the southern and the western fronts still have a ways to go. The forces that are fighting against ISIS in those areas are not on the outskirts of the city. The counterterror forces are pushing into the eastern area on their own. But there's no doubt that this is a huge psychological moment for Iraq. Mosul fell to ISIS more than two years ago, almost without a fight. It was a colossal failure to the army and the federal police who were holding the city at the time. So people here have been waiting for this moment, also somewhat anxiously.

MONTAGNE: And the U.N. has been saying that the Islamic State has taken thousands of villagers into the city to serve as human shields. Are you seeing any sign of that yet?

FORDHAM: Yeah, Renee. We have actually been able to reach people inside Mosul who say that they have, indeed, seen and spoken to people who have been forcibly displaced from villages south of the city and brought up to Mosul. They're living in abandoned buildings now. They said that they were tricked into coming. They were told they'd only be leaving their homes for a short time.

We presume that they will be used as human shields. That's something that I've seen myself before in another Iraqi city, Ramadi. And ISIS have done this in other places. And people inside Mosul confirmed to us also that there are thousands of ISIS fighters there. They have erected defenses, and they have dug tunnels under houses that we now know go on for miles in some cases.

MONTAGNE: Well, it sounds as though this will be a very harsh, urban combat situation once Iraqi forces actually enter the city. Is there a way to know how it will play out?

FORDHAM: Yeah. The counterterror forces along with the Iraqi army and the Kurdish forces known as Peshmerga on this eastern front, thus far, have been fighting their way through depopulated areas. There's still been considerable resistance from ISIS. But fighting in a populated, urban area is much more difficult.

And I've been through some of those villages that have been retaken. The destruction that is striking. So all the indications are that it is going to be worse inside Mosul. The assumption is that ISIS will fight hard for this. This is their most prominent, their most popular city. And accounts from inside the city suggest ISIS still have support there. There's a long-term mistrust of Iraqi authorities inside Mosul.

MONTAGNE: Well, Alice, thanks very much.

FORDHAM: Thanks for having me, Renee.

MONTAGNE: NPR's Alice Fordham speaking to us from Erbil in northern Iraq. Transcript provided by NPR, Copyright NPR.