In the days before Christmas, Iraqi ground forces entered what a US official called an "operational refit," temporarily pausing their ground operations against ISIS' last Iraqi stronghold in Mosul.

But while Iraqi ground forces took a breather, the US-led coalition air campaign against the terror group continued. In a December 23 strike, coalition air forces knocked out an ISIS weapons cache near Mosul, which is Iraq's second-largest city.

Three airstrikes on December 23 targeted ISIS tactical units, ISIS buildings, fighting positions, a vehicle and a vehicle-borne improvised-explosive-device factory, and weapons systems.

The offensive against Mosul was paused after a little more than two months of fighting — a period during which Iraqi forces, aided by Kurdish peshmerga and Shiite militias, had recaptured just one-quarter of the city.

The campaign was renewed on December 29, when Iraqi army, counterterrorism forces, and police moved forward on the north, east, and south of the city.

US soldiers gather near military vehicles at an army base in Karamless town, east of Mosul. Ammar Awad/Reuters

Iraqi forces have since retaken several more neighborhoods in eastern Mosul.

The top commander of Iraq's elite Counter-Terrorism Service, which has spearheaded the fight against ISIS in Mosul, said Iraqi forces had retaken "more than 60%" of the eastern side of the city.

Iraqi forces have yet to enter the western side of the city.

And, according to a US official, ISIS forces were beginning to show the strain of the fight.

"They've got a finite amount of resource that are on the eastern side and the fact that their capability is waning indicates that those resources are starting to dwindle," US Army Maj. Gen. Joseph Martin, head of ground forces for the US-led coalition fighting Islamic State, told Reuters on January 2, citing the decreased sophistication of ISIS suicide bombs and the lower yield of the group's improvised explosive devices as a sign "the enemy's capacity is diminishing over time."

"We see that as a positive indicator," he added.

The suffering faced by the 900,000 or so Iraqis stuck in and around the city is unlikely to diminish as long as there is fighting going on, however. Many residents of the city have elected to shelter in their homes, staying indoors for days at a time.

Others have the arduous trip out of the city, dodging running battles between Iraqi forces and ISIS militants punctuated by artillery fire and ongoing airstrikes.

Iraqi people flee the ISIS stronghold of Mosul in al-Samah neighborhood, Iraq, December 2, 2016. Reuters/Mohammed Salem

On January 1, US-led strikes against ISIS targeted an ISIS mortar position next to two empty school buildings. Though the coalition said no civilians were in the area during that strike, two days prior a van carrying ISIS fighters was hit by a coalition strike while in the parking lot of a hospital compound. The coalition said it was investigating possible civilian casualties.

Iraqis in the western half of Mosul have started to flee across the Tigris River, which bisects the city. The two halves of the city were once connected by five bridges, but those spans have all been destroyed, and Iraqis now wait until nightfall to cross by boat or to scale the remains of the bridges with rope.

"Only the lucky ones get out," Jamal, who crossed the remnants of one bridge using a rope and is now at a camp for civilians displaced from Mosul with his wife and three children, told Reuters. "If they opened a route for a quarter of an hour, not a single person would remain on the western side."

While thousands of ISIS fighters remained hunkered down in Mosul in northern Iraq, the terror group has been able to strike farther south.

At least seven people were killed by an ISIS attack on a police checkpoint on Sunday, and a suicide car-bomb attack in Baghdad — parts of which are regularly targeted by ISIS — killed at least 17 people on Monday.