MOSUL, IRAQ (NYTIMES) - The fighting is all but over in Mosul, and the billboards are already up: hastily raised signs in which the government urged the city's Sunni residents to "turn the page" from the terrorists of the Islamic State in Iraq and Syria (ISIS) group.

As Iraqi Prime Minister Haider al-Abadi visited Mosul to declare victory and call for unity, civilians on the longer-secured east side of the city danced and waved Iraqi flags. Some called for brotherhood between Sunnis and Shi'ites, or chanted, "By our souls and blood, we sacrifice for you, Iraq!"

It is a moment for Iraqis to celebrate after nearly nine months of bloody warfare against the Sunni extremists of ISIS. But despite the flaring of hope for a new national unity, the government's costly victory in Mosul and the questions hanging over its aftermath feel more like the next chapter in the long story of Iraq's unravelling.

Most pressing is the need to bring back hundreds of thousands of displaced Sunni civilians. And the stark failures of that process in some other places freed from ISIS make clear that the process here carries both great importance and great risk.

Reports of past abuses by the Shi'ite-controlled government and its security forces and militia allies against Sunni families have kept sectarian divisions fresh. And with no sectarian reconciliation process to speak of, any setback in the resettling of Mosul could dangerously add to the list of grievances.

For the mostly Sunni residents of Mosul, there are the devastating after-effects of living under ISIS, also known as ISIL or Daesh. And there is deep doubt and fear over what will happen to them next.

"The people of Mosul need to be psychologically treated and rehabilitated through long-term programmes," said Intisar al-Jibouri, a Member of Parliament from Mosul. "They have lost family members, been tortured, beaten for silly reasons by ISIS."

Concerns are growing that Shi'ite militias that mobilised in other parts of the country to fight ISIS could turn their guns on one another in a scramble for power. And the thoughts of many in Iraq's Sunni community have stayed fixed on revenge against their neighbours who supported ISIS, with increasing reports of violent reprisals.

The Kurds, who have operated an autonomous enclave in the north since the 1990s, are moving quickly to hold a referendum on independence in September, despite pleas from US diplomats to hold off.

So, the end of the Mosul battle, even with ISIS still in control of other areas of the country, resurfaces a vital question that has been asked ever since the modern and multi-sectarian state of Iraq was created from the ashes of World War I: Can the country hold together?

At great cost in lives and property, Iraqis have shown that they can defeat ISIS militarily. But whether they are up to the political challenges to bring the country together again - or even get the lights turned on in Mosul, or bring the displaced back home, for that matter - is another question entirely.

"Right now, we are only fighting Daesh militarily," said Jabar Yawar, secretary-general of the peshmerga, the Kurdish security forces in northern Iraq.

As for politics and governance, Yawar, whose men participated in the early phases of the Mosul battle last fall, said: "There is nothing, no plan. We are fighting, and that's it."

Hoshyar Zebari, Iraq's former foreign minister, a Kurd originally from Mosul, said: "Everyone is in a hurry to achieve a military victory, without regard for the destruction or the day after."

Zebari is now working to support the Kurdish referendum, which is likely to go forward despite objections from the United States, Turkey and Iran. Most expect a resounding "yes" vote, given the depth of feeling among Kurds to have their own state.

"Forget Kurdistan," said Masrour Barzani, chancellor of the Kurdistan Region Security Council and the area's top intelligence official. "Is the rest of Iraq united? Even the Arabs in Iraq are not united." He continued: "We are not the reason Iraq is falling apart. I think Iraq is a fabricated state. It was built on the wrong foundations."

And then there is Syria. The civil war across the border, as much as the sectarian policies of former prime minister Nouri al-Maliki helped ISIS regenerate in Iraq after its predecessor, Al-Qaeda in Iraq, was largely eradicated. The group was able to expand into Syria before sweeping across the border in 2014 and taking Mosul.

Without peace in Syria, officials say, there is little chance for peace and stability in Iraq.

"Syria and Iraq are closely connected," Maliki said in an interview this year. "If the situation in Syria is unstable, Iraq will be unstable."

When asked about the future of Iraq after ISIS, Maliki said: "The state cannot control the situation. The coming phase will be bad."

With the larger questions hanging over the country, the immediate challenge of stabilising Mosul is monumental, especially in the city's west side. The fight has essentially turned the city into two, divided by the Tigris River. The west is a gray, dusty wasteland of flattened buildings and upturned, charred trucks; even the windows of the cars civilians are driving have been blown out.

Cross the bridge, though, and suddenly the world emerges in light and colour, with shops and restaurants open, and loud traffic jams.

Fighting continued on Monday in a small patch of the old city, and security forces there rescued two more girls from Iraq's Yazidi religious minority who had been held as sex slaves. The United Nations, meanwhile, put out an urgent call for funding from other nations to help the nearly 700,000 civilians still displaced from the fighting.

All day long on Monday, Iraqi state television played patriotic songs in honour of the security forces, and later in the evening, a news flash alerted that al-Abadi would make a "historic" speech, surrounded by soldiers. The prime minister, once again, declared victory in Mosul, saying, "Iraq is now more united than ever," and he declared Tuesday a national holiday of celebration.

And in the skies over Mosul, Iraqi airplanes dropped three million leaflets on a city where many of the residents are no longer there.

Each leaflet showed a map of Mosul in the colours of the Iraqi flag - red, white and black - with the message: "Mosul has been returned to the bosom of Iraq."