Watch a US-led coalition strike destroy an ISIS vessel near the terror group's Iraqi stronghold

The Iraqi forces struggling to retake the country's second-largest city, Mosul, from ISIS have paused their advance, entering what a US official called an "operational refit."

That halt comes after two months of hard fighting, during which Iraqi forces and their allies have pried just one-quarter of the city away from the 4,000 or so ISIS militants hunkered down there.

A US-led coalition has supported Iraqi forces throughout the campaign, including a November 16 strike that destroyed an ISIS watercraft - vital for navigating Iraq's extensive rivers - near Mosul.

Coalition-led airstrikes near Mosul on November 16 targeted four watercraft, destroying them as well as six mortar systems, two fighting positions, two vehicles, a bunker and an ISIS held-building. Those strikes also targeted tunnels and tactical units.

Mosul is bisected by the Tigris River and had five bridges connecting the eastern and western halves of the city. ISIS militants in the city mined and booby-trapped the bridges, and as of late November four of the five spans had been destroyed.

Google Maps

Mosul, outlined in red, is connected by five bridges, show in black.

The US-led coalition has gone after ISIS watercraft on numerous occasions, particularly in the run up to the Mosul campaign, which kicked off in mid-October.

In September alone, coalition warplanes destroyed 65 boats, which ISIS has used both as a means of transport and as a way to mount improvised explosive attacks.

Boats have also figured into ongoing fight for control of Mosul and its environs. On September 14 and 16, strikes near the towns of Qayyara and Sultan Abdallah, which are south of Mosul on the Tigris River, destroyed more than 50 boats.

The Iraqi campaign has so far only recaptured about one-quarter of Mosul from ISIS, and the terror group has maintained some freedom of movement to launch counterattacks, mounting vehicle-borne suicide improvised-explosive-device attacks with relative alacrity.

REUTERS/Goran Tomasevic

An Iraqi special-forces soldier shouts in front of a burning house after an ISIS suicide car-bomb attack against Iraqi special forces during clashes in Mosul, Iraq, November 19, 2016.

When the operation against ISIS in Mosul began, there were believed to be about a million civilians caught in the city. In the weeks of fighting, tens of thousands have been displaced, but many more remain in contested parts of the city or in areas under ISIS control.

Civilians are frequently caught in the crossfire, in some instances allegedly from coalition or Iraqi government forces. Even civilians in liberated parts of Mosul are not safe from the fighting.

Iraqi officials have not released statistics about those killed and wounded in the Mosul offensive, but the UN warned in mid-November that civilian casualities were overwhelming Iraqi government and international aid groups in the area.

"Since then, the situation seems to have deteriorated," Reuters reported this week.

You can see the full video of the November 16 strike below.