Col. Refaq Abdul Baqi paused for an instant at a cinder-block wall before darting across the alleyway. Safely through, he crouched low as he climbed the stairs to the roof of a dilapidated house on the edge of this city's Qubbah district.
"This is the right bank of Mosul," said Baqi, gesturing toward the set of tranquil-looking hills just across the nearby Tigris River. Behind them stands the last redoubt of Islamic State jihadists, who for 2½ years have ruled Mosul and made it a key center of their self-proclaimed Caliphate.
In January, the Iraqi government announced it had "completely liberated" the city's eastern half. But it had been a ferocious fight: The militants had dispatched waves of car bombs and suicide attackers, forcing government troops to halt their offensive on the edge of the Tigris, which bisects Mosul.
Now, after almost a month of retooling, they are poised to begin a three-pronged assault for the city's western side.
On Friday, Iraq's Counter Terrorism Service, an elite U.S.-trained group also known as the Golden Division, began an intense mortar barrage on the right bank as engineering crews prepared to install pontoon bridges. (The U.S.-led coalition bombed the five bridges connecting Mosul's two sides during the initial assault on the city to restrict the jihadists' movements.)
Meanwhile, emergency responders and federal police units have mustered in the village of Areyj. In an off-limits corner of the village, camera-shy American and Canadian special forces units operate reconnaissance drones from trucks bristling with antennae.
Once the signal is given, the forces there will begin the seven-mile trek to the Mosul airport on the southern edge of the city, in an advance that is expected to take one week.
The battle for the western districts promises to be even more challenging than the offensive for the eastern half, which took 100 days and reportedly produced to casualty rates as high as 50% for some units.
"The right side is older, with buildings close together. It's a problem," said Abdul Baqi, rattling off names of neighborhoods with some of his subordinates.
"Some of the alleyways are the width of a door. You can't bring in anything except infantry, while soldiers go on the rooftops to reconnoiter."
The jihadists have also had time to entrench themselves, said Col. Mohammad Wakaa, a spokesman with Nineveh Operations Command.
"They have opened up holes from house to house so they can move undetected," he said, adding that most of the foreign fighters who have joined Islamic State from outside Iraq, thought to be among the movement's most extreme adherents, have retreated to the western side.
"We believe the die-hard combatants, those who won't give up, are roughly 400. We expect the others will run away," Wakaa said.
The United Nations warned Saturday that the estimated 750,000-800,000 people in western Mosul are at "extreme" risk due to dwindling food and fuel supplies, as well as acute shortages of drinking water and electricity.
"People in the eastern part of the city had been terrorized before the offensive, yes, but they were not in the same dramatically dire circumstances that we believe those in the west to be," said Lise Grande, the U.N.'s humanitarian coordinator for Iraq, in a phone interview Saturday.
Still unclear is how much support Islamic State militants still have around the Old City quarter, which the U.N. says is home to an estimated 400,000 people.
After Islamic State's stunning blitz through Mosul in mid-2014, the city's mostly Sunni Muslim population appeared jubilant. They called the militants revolutionaries who had defended them against the Iraqi army, which many said had been transformed under former Iraqi Prime Minister Nouri Maliki into Shiite death squads.
But the jihadists' welcome soon morphed into fear after the group began to mete out atavistic punishments, such as amputations and beheadings, against those who violated its interpretation of Islamic scripture.
"The Old City, where people are poorer, is historically known for its support of Al Qaeda and now Islamic State," said Maj. Gen. Thamer Ismail, head of the Emergency Response Division, in an interview Saturday.
Ismail said his troops had seen militants ferry civilians in the past few days to areas previously emptied of residents in a bid to use them as human shields.
In the aftermath of the offensive for eastern Mosul, aid agencies lauded Iraqi forces for their restraint. The troops relied mainly on small-arms fire and avoided needless destruction of property and killing of civilians.
"If you look at the military pattern of the campaigns over the last year, every time, the populations fled. In Mosul, 550,000 people remained. It was unexpected," said Grande.
Almost 190,000 escaped the fighting to refugee camps set up around Mosul. Roughly 46,000 have already returned to the city, where many neighborhoods, especially those on its eastern outskirts, appear to be normal, save for the occasional grenade-dropping drone or mortar lobbed by Islamic State.
"It was unexpected, and it has meant that the recovery process has gone much faster," Grande said.
That restraint, however, may be harder to maintain in the high-density areas of western Mosul. The assault could trigger an outflow of civilians that would overwhelm aid groups, Bruno Geddo, the United Nations High Commissioner for Refugees' Iraq representative, said in an interview Friday.
"The liberation of Mosul is necessary but not sufficient. We have to get the humanitarian response correctly … only then can we counter the toxic narrative of ISIS," he said, using an acronym that refers to Islamic State.
"Therefore, up to the last day, we have to be on guard, because if you get something wrong, then the whole thing will be perceived as a failure."
Special correspondent Haidar Abdul Ilah contributed to this report
Bulos is a special correspondent.