The Iraqi military's operation to retake the northern city of Mosul after more than two years of occupation by the Islamic State in Iraq and Syria (ISIS) could require months, even with American help.
But the recapture may turn out to be the easy part. If history is a guide, vast parts of Mosul, once Iraq's No. 2 city with about two million inhabitants, could be left in smouldering ruins by retreating or die-hard ISIS fighters who may use remaining civilians as shields and booby-trap entire neighbourhoods with improvised bombs. Just clearing these explosives could take months or years.
Three other important Iraqi cities recaptured from ISIS - Ramadi, Tikrit and Fallujah - were left in varying degrees of devastation.
Here is a look at what happened to each.
Captured by ISIS: May 2015
Recaptured by Iraqi military: December 2015
Ramadi, the capital of heavily Sunni Muslim Anbar province, about 112km west of Baghdad, once had a population of at least half a million.
Although occupied by ISIS for only half a year, much of the city was obliterated in the Iraqi military's campaign to retake it, which included bombing runs by US warplanes and combat with ISIS fighters who created a network of tunnels and hideouts. Many residents fled, staying in camps for internally displaced people administered by the United Nations and other aid groups.
Today, 10 months after Iraq's Shi'ite-led government proclaimed Ramadi liberated, parts of the city remain unlivable because of bombs and other remnants of war ensconced in the rubble or placed in vacant schools, homes and hospitals.
Ms Lise Grande, the top UN humanitarian aid coordinator in Iraq, said about 300,000 people had returned to Ramadi, but basic services had not been fully restored.
Captured by ISIS: June 2014
Recaptured by Iraqi military: April 2015
Tikrit, Saddam Hussein's hometown, about 160km north of Baghdad, was the first major test of the Shi'ite-led government's ability to repopulate Sunni areas taken from ISIS. The effort went relatively well: Most of the roughly 150,000 residents who had fled returned within a few months.
The first returnees, however, found a city with no services. Shi'ite militiamen had looted parts of Tikrit, the main hospital was destroyed, and unexploded ordnance lurked in areas ravaged by combat.
The government opened bakeries and provided residents with rice and cooking oil. Shi'ite militias even escorted displaced Sunni families back to their homes, and security in the city was quickly turned over to local Sunni men.
The government had a hand in reconciliation efforts between tribes, in which blood money was paid to settle feuds from when ISIS was in control.
Captured by ISIS: January 2014
Recaptured by Iraqi military: June 2016
Fallujah, a restive Sunni-dominated city less than 64km from Baghdad, was the first to fall to ISIS and has been an important incubator for Sunni extremism.
The Iraqi effort to retake Fallujah left it less devastated than Ramadi.
Even so, weeks of indiscriminate shelling by Shi'ite militias, as well as fierce fighting in the final weeks of the assault, left sections of the city in rubble.
Before Iraqi forces proclaimed victory in June, officials estimated that 90,000 civilians were in Fallujah; the city's population at its height was close to 300,000. Ms Grande said more than 70,000 had since returned.
Once recaptured, Mosul could pose a far more complicated rebuilding challenge, given that it is so much bigger than other ISIS conquests and was much more diverse, with Christian, Kurdish and Shi'ite minorities.