On the western side of Mosul, much of the fighting against Islamic State militants takes place between houses so close that they almost touch. Snipers fire from roofs and through holes blasted into outer walls.

Seen through these holes, this part of Iraq's second-largest city is a landscape of half-collapsed buildings, burned-out cars and rubbish-strewn streets. Helicopters hover and barricades of sandbags block the streets.

This front line near the old city is where police officer Mayser Suleyman Karim marked his 33rd birthday with the rest of his unit.

The Islamic State extremists who took over the city in 2014 were driven out of eastern Mosul by Iraq's elite counterterrorism force in January. Much of the fighting in the city's western districts, however, has been done by the heavily militarized federal police force.

During a momentary pause in the battle, Mayser recalled that he had joined the force in the aftermath of the mosque bombing in Samarra on Feb. 22, 2006. That's when suspected al-Qaida militants blew up the al-Askari shrine, one of the holiest in Shiite Islam, starting a wave of sectarian violence in which thousands died.

"It has been a long time now — 10 years. No, 11 years actually. I'm tired," Mayser said apologetically.

"For how long can you keep doing this?" he asked. "Your joints start to hurt, movement is difficult, cannot run. ... It's not about being scared, I'm just getting tired. My body is getting tired."

Part of the police unit's work in western Mosul involves manning checkpoints and interacting with civilians, some of whom remain in the area despite the fighting.

Many police are instinctively wary: They come from distant parts of Iraq, know little of Mosul and suspect that militants or their supporters might have blended into the population. Security forces have been hit by suicide attacks from the militants.

Mayser said he wanted to quit his job but didn't have any options at the moment.

"It's good that I'm not married. But there are guys here who are married and have kids. Their situation is more difficult than mine," he added.

The police unit sometimes harasses militants by firing mortars at them over the buildings. That's one reason the city has been wrecked so badly.

According to a terrain analysis done by the United Nations, there is about 2½ times more destruction in western Mosul than in the eastern half, and the extremists have not been fully driven out of the west yet.

Government artillery units also pour vast amounts of fire into the parts of the city under IS control. Airstrikes target snipers, sometimes bringing down several buildings in the hunt for a single militant.

It is hard to be sure how many civilians have been killed or wounded since the battle for western Mosul began nearly two months ago.

The U.N. said at least 300 people have been killed, while the Nineveh provincial health department reckons that the real number could be closer to 1,000. At least 1,600 cases of trauma have been admitted to Iraqi and Kurdish hospitals since Feb. 18.

After a day's work, the police unit returned to its base, and the men collapsed onto broken chairs and sofas.

Mayser said the brutality of the war — seeing friends get killed or wounded — had made him stronger. But it has also made him less sensitive to suffering.

"Now I'm ignoring everything that happens, no matter how small or big. Your mother or your father getting ill, things like that, I've seen worse than this," he said.

The unit spends 20 days on duty and 10 days off. The time has come for their leave, and the men have packed their weapons away, preparing to depart.

On their last day of duty, it began to rain. Standing in the door of their base to watch the rain, one of them recalled nearly getting hit by a car bomb. He laughed at the absurdity of the experience — but also, no doubt, in relief.

The rain intensified, but the men were determined to go home. With their assortment of umbrellas, rain jackets or blankets used for cover, they joked and laughed as they splashed through puddles of water and ran giddily through the downpour.