GWEN IFILL: The Iraqi government last week announced the beginning of what it said is the campaign to free Iraq's second largest city from ISIS control.

Mosul was overrun nearly two years ago and has become a vital hub for the group's operations in Iraq. But whether Iraq's military is up to the challenge is an open question, even as the potential grows for deeper American involvement.

Special correspondent Jane Ferguson reports from the front lines near Makhmour, Iraq.

JANE FERGUSON: In an effort to soften ISIS positions, Iraqi forces bombard them repeatedly. They are trying to push forward from this sandbank up the hill to a village Islamic State fighters are dug into.

Last week, the Iraqi army suddenly announced the launch of the long-awaited battle for Mosul city. In reality, so far, just several villages have been retaken in the Makhmour area, well south of Mosul.

This is as far as the front line comes for these Iraqi troops. They are mortaring the village in that direction that is just on that hill. It's about half-a-kilometer from here. And that's where ISIS positions are. That village is called al-Nasr. They plan to then move in and try to occupy the village, but they have been trying to do that for three days.

Far beyond that village is the city of Mosul, and bit by bit, inch by inch, they plan to retake it. So far, progress is slow. Iraqi forces swiftly abandoned their positions here in 2014, when ISIS swept across the country.

Morale in the military has yet to fully recover. So, when Iraq's commander of ground forces, Lieutenant General Riyadh Jalal Tawfiq, showed up near the front lines in an unexpected visit, there was great fanfare. But he didn't wish to talk about past mistakes.

When ISIS took Mosul Iraqi forces quickly withdrew from the city when ISIS were moving quickly. How do you feel like you can prevent that happening again?

MAJOR GEN. RIYADH JALAL TAWFIQ, Iraqi Army (through interpreter): These issues depend on the time frames and plans designed for them. After that, for every incident, there will be a response. If God wills it, we will retake Mosul.

JANE FERGUSON: The battle lines in Iraq are as complex as the country's woven identities. Iraqi forces are holding this ground alongside Kurdish fighters called Peshmerga. They are a skilled fighting force, protecting the semiautonomous Kurdish region, which borders Mosul. They are holding the line on both ends of the Iraqi army.

Peshmerga fighters are supported by U.S. airstrikes when they confront ISIS, but are not given the extensive military equipment the official Iraqi army receives from America. This Peshmerga commander, Colonel Naji Bedaroni, wandered over to inspect their progress.

He wasn't impressed.

COL. NAJI BEDARONI, Peshmerga (through interpreter): The operation is very weak. It's not strong enough. I believe that if the Peshmerga had the equipment they have, we could liberate this village in three to four hours, not three to four days.

JANE FERGUSON: Kurdish forces have pushed ISIS out of most of their areas. An agreement for them to take part in the battle for Mosul, a mostly Arab city, has yet to be reached. But without the Peshmerga, the Iraqi army will struggle to retake the city alone.

Are the Peshmerga taking part in this fight?

COL. NAJI BEDARONI (through interpreter): For this, we need a political decision. That area that is being targeted for this operation is not a Kurdish area. We are just guarding our bunkers. If we get orders, for sure we can do that, but, until now, we have not gotten any orders.

JANE FERGUSON: How is the relationship between the Kurdish Peshmerga fighters and the Iraqi army?

COL. NAJI BEDARONI (through interpreter): We are coordinating with them. We are helping them. But they are weak. They don't believe strongly in the cause.

JANE FERGUSON: Soon, we are on the move, to another part of the battlefield. Unseen on this front line, but still playing a major role, are U.S. forces, providing advise and assist and support for Iraqi and Kurdish forces.

An American Marine was killed earlier this month, not long after arriving at a base in here in Makhmour. Only after his death did the U.S. military announce the presence of the Marines.

Chairman of the Joint Chiefs of Staff General Dunford admitted last week there will be more U.S. boots on the ground soon.

GEN. JOSEPH DUNFORD, Chairman, Joint Chiefs of Staff: We have a series of recommendations that we will be discussing with the president in the coming weeks to further enable our support for the Iraqi security forces.

So, again, the secretary and I both believe that there will be an increase to the U.S. forces in Iraq in the coming weeks, but that decision hasn't been made.

JANE FERGUSON: The U.S. military in Makhmour declined requests from "PBS NewsHour" for an interview.

Fighting between ISIS and the Iraqi army and Kurdish forces has flattened village after village here. The scenes are of complete devastation. Civilians are running from their homes where the fresh fighting has broken out. These people came from the villages recently retaken from is, seizing the chance to escape the fighting.

We have just come upon this scene here of civilians fleeing the frontline. Further back there, as far as the eye can see, where cars are coming from, there are several villages where ISIS have either retreated or have been pushed out by Iraqi forces. Civilians are fleeing while they can, anticipating perhaps more maneuvers.

Not everyone is jubilant. Traumatized and exhausted, these women and children arrived at another front-line position while we were filming. They ran from their village as ISIS retreated. A girl was killed. We are told ISIS shot her as she ran away. This elderly woman said they were being held as human shields.

"The ISIS were wearing explosive belts and we couldn't leave because of them," she cries.

Where are the men?

WOMAN (through intepreter): They wouldn't let them leave because they were police and army. They slaughter. They took seven from my family.

JANE FERGUSON: This outpost is manned by another group involved in this offensive, Hashd al-Shaabi, or Popular Mobilization Fores. They are militia, and quickly descend into fighting with the official army commanders accompanying us.

In other areas retaken from ISIS like Ramadi and Tikrit, such forces are predominantly Shia, but, here, we are told these men are Sunni tribesmen. We are told to leave.

On this battlefield, it's not always clear who's in charge. The fight to retake Mosul from ISIS will be the toughest yet. Losing the city could be a deadly blow for the terror group. Given the chaos of this battle's earliest stages, a quick victory seems out of reach.

For the "PBS NewsHour," I'm Jane Ferguson in Makhmour, Iraq.