Irbil (CNN) The terrifying scene has played out time and again. Amid a chaotic battlefield, an unknown vehicle barrels across the Nineveh plains, kicking up clouds of dust in its wake. It's speeding toward Iraqi or Kurdish Peshmerga front lines with a cargo of high explosives. Soldiers fire rockets and missiles in a frantic effort to destroy the vehicle before it kills them. Sometimes they find their target; sometimes not.

ISIS forces hit the positions of Iraqi Kurdish Peshmerga fighters during an operation to recapture Nawaran village on October 19.

In the first week of the Mosul campaign, there have been dozens of suicide vehicle attacks by ISIS. Those that have got through have caused many casualties. ISIS has deployed its full repertoire: snipers, booby traps, a web of tunnels for ambushes.

In some places, it's taken Iraqi and Kurdish forces days to clear villages -- but they have made progress taking an area of several hundred square kilometers from the east, north and south.

A Peshmerga fighter peers up from an underground tunnel in the liberated town of Badana on October 18. ISIS built tunnels below residential streets to escape from airstrikes.

Most of the advances have been through the Nineveh Plains to the east of Mosul, an area abandoned by its largely Christian population after ISIS seized Mosul in June 2014. Advancing forces have been supported by intense airstrikes -- the heaviest since the campaign against ISIS began.

Some people have begun to return to see what happened to their towns after two years of ISIS occupation. In the Christian town of Bartella, the church bell rang again, and the local priest surveyed the desecration of tombstones. But they can't move back because of the danger of booby traps and destruction of basic services.

An Iraqi soldier walks past a broken statue of the Virgin Mary in the predominantly Christian village of Bartella on October 23.

One man leaving his village told CNN: "We can't live there -- there's no water, electricity, damage everywhere and explosives."

Closing in

Forward units are now -- in some places -- seven kilometers from the outskirts of Mosul. Kurdish Peshmerga have begun to dig a long trench and berm to mark their front line.

Next, it will be up to the Iraqi Golden Division and other units to take the fight to the city itself. And that fight will become tougher in a dense urban environment, which ISIS has spent two years fortifying and where it will likely use civilians as shields to deter airstrikes.

A boy pauses on his bike as he passes an oil field that was set on fire by retreating ISIS fighters ahead of the Mosul offensive, on October 21 in Qayyara.

Progress from the south has been a harder slog. Iraqi forces are moving up the Tigris river and said Monday they are close to the town of Hamam al-Aleel, which sits on a bend in the river some 20 kilometers south of Mosul. The advance has been complicated by fires set at oil wells by ISIS and by a blaze at a sulphur plant.

The World Health Organization said Monday that it's helping treat more than 1,000 cases of suffocation caused by the smoke from the Al Mishraq sulfur factory.

ISIS is doing its best to complicate the battlefield by launching attacks as far afield as Kirkuk , a Kurdish-held city south-east of Mosul, and the town of Rutba in the far-west of Iraq. It's a long-held tactic of the group -- divert and distract.

A view of Kirkuk is seen through the broken window of Jihad Hotel on October 22. ISIS used the hotel as a base during an attack in Kirkuk on Friday.

The attack in Kirkuk last Friday, which involved several dozen militants, served another purpose: to sow suspicion between Kurds and Arabs in the city. Some Kurdish officials claimed that Sunni Arabs among the large displaced population in Kirkuk had helped the ISIS militants infiltrate the city.

ISIS fighters have also hid in villages while army units have passed. In one, near the ancient ruins of Nimrud, they watched as local people greeted troops. When the troops moved on, the militants emerged and killed 40 people who had dared to welcome liberation.

Resistance inside Mosul

Clandestine phone calls from inside Mosul provide fragments of information. There are the first signs of open resistance to ISIS.

Witnesses inside the city told CNN Monday that a gun battle had broken out overnight in Wadi Hajer neighborhood and had lasted an hour. Later, ISIS arrested a number of people in the area, which is on Mosul's southern outskirts.

There is no way to verify the report, but if true it would mark more bolder resistance than the sporadic assassinations to date. One source told CNN that he expected more resistance as the offensive approached the city gates.

An Iraqi forces member helps a man push a car as they arrive at a refugee camp on October 22, in the town of Qayyara.

ISIS has warned civilians in Mosul that anyone caught with a cell phone will be summarily executed, and told the population that they will fight to the death, even as they send their families across the desert toward Syria.

There is evidence to support that. The stream of civilians leaving Mosul so far have mostly fled toward ISIS-held parts of western Iraq. A tribal leader from the border area, Sheikh Abdullah Alyawer, told CNN that hundreds of ISIS militants and civilians had crossed into Syria near Ba'aaj, an ISIS-held town. Many of the civilians are then heading north to a ramshackle camp just inside Syria at al Hawl.

People flee

Karl Schembri of the Norwegian Refugee Council said some 900 people had fled to Syria and described the situation at al Hawl as very grim, with conditions "below basic." The United Nations does not have direct access to the camp. An estimated 50,000 Iraqi refugees may enter northeastern Syria in the coming weeks, through a route that has not yet been cleared for landmines.

Elsewhere, civilians are emerging from olive groves or silent villages -- waving white rags -- and describing the nightmare of life under ISIS. Many are hungry and have been without clean water supplies for days, according to aid agencies.

One young girl met by Peshmerga forces shyly presented soldiers with a flag she had drawn. She said she didn't like ISIS because they had not let her go to school, forced her to wear a hijab and had killed people to take over their homes.

Displaced families gather in an area near Qayyara on October 24.

Altogether, aid agencies expect around 200,000 people to flee Mosul in the first weeks of the offensive.

Hundreds -- perhaps thousands -- more civilians have been less fortunate, driven toward Mosul by ISIS fighters as they retreat, corralled into an ever shrinking killing zone. Their arrival in the city will put even more pressure on limited food and energy supplies.

What happens next

Long before Mosul is liberated, attention is already turning to the "day after." During his visit to the region at the weekend, US Defense Secretary Ash Carter said he was already thinking ahead to the desperate need for stabilizing Mosul.

"It's very important...the security forces sustain the peace," he said. "We need to make sure the non-military campaign doesn't lag behind the coalition military campaign."

That non-military campaign involves making Mosul liveable again -- but also making it governable. Integrating the various militia that have sprouted since Mosul fell to ISIS, devising better governance for the city, are challenges as great as liberating it in the first place. There may be turf wars.

A member of Iraqi forces gestures towards the frontline on October 18, near the town of Qayyara, during an operation to recapture the city of Mosul from ISIS.

US and Iraqi officials have spoken of creating eight self-governing areas in and around Mosul. Ever since Iraq's new constitution was passed, there's been much talk of local autonomy, but it's rarely been delivered.

To many observers, Mosul will be the acid test of Iraq's viability -- and whether its mosaic of sectarian, tribal and ethnic groups can live in peace, if not harmony.