Watch a US-led airstrike destroy an ISIS headquarters building near the group's urban stronghold in Iraq

REUTERS/Zohra Bensemra

A Federal police member flashes victory sign in the liberated part of Albu Saif village south of Mosul, Iraq, February 21, 2017.

The fight to liberate the Iraqi city of Mosul from the clutches of ISIS is poised to enter its sixth month.

And Iraqi forces in recent days have advanced on the western half of the city, the last part of Mosul still held by the terrorist group.

A coalition of more than 60 countries, led by the US, has assisted the Iraqi government's efforts since the beginning of the Mosul campaign in October, targeting ISIS weaponry, equipment, and infrastructure across northern Iraq.

In a January 9 strike, show below in footage released by the US Defense Department, an airstrike levels a building believed to be an ISIS headquarters near Mosul.

The January 9 strike was one of 11 conducted in Iraq that day. A total of seven strikes took place near Mosul, targeting ISIS tactical units, fighting positions, ISIS-held buildings weapons, tunnels, and several vehicle-borne improvised explosive devices and a facility producing them.

The terrorist group has relied heavily on VBIEDs through the fighting in Mosul, using them with deadly effectiveness in the cramped confines of the city's historic neighborhoods and narrow streets.

REUTERS/Alaa Al-Marjani

Displaced Iraqis flee their homes during a battle with ISIS militants, in district of Maamoun in western Mosul, Iraq, February 23, 2017.

Some 750,000 civilians are believed to still be in western Mosul, and tens of thousands have already fled the city amid the fighting.

The Iraqi offensive against western Mosul started on Sunday, and government forces have since retaken several villages and desert areas near that section of the city.

On Friday, Lt. Gen. Sami al-Aridhi, of the country's elite Counter-Terrorism Service, said his forces had captured a military base and village southwest of the city and had entered a residential neighborhood in western Mosul for the first time since the campaign started in October.

"We have attacked and fully control Ghazlani base, we have also taken Tal al-Rayyan... and we're attacking Al-Maamun neighbourhood," he told AFP.

Iraqi forces have also reportedly taken full control of the city's airport, which is just south of the western half of Mosul.

REUTERS/Alaa Al-Marjani

Iraqi army launch a rocket toward ISIS positions during a battle with IS militants near Ghozlani military complex, south of Mosul, Iraq, February 23, 2017.

Quentin Sommerville, the BBC's Middle East correspondent, was with Iraq's Emergency Response Division as it pushed into western Mosul amid thick plumes of dark smoke from fires set by ISIS militants trying to obscure their movements.

Photos he posted showed laundry still drying outside homes in the city.

"Now the real fighting starts," Col. Amer Sabar Gyad, of the ERD's 1st brigade, told Sommerville as Iraqi forces entered the city.

While ISIS is expected to put up fierce resistance in the tight confines of western Mosul's ancient neighborhoods, coalition commanders have expressed optimism about how the fighting in the city will progress.

But even if the city is quickly retaken, the fight with ISIS and its remnants will drag on elsewhere.

Gen. Joseph Dunford, the chairman of the US Joint Chiefs of Staff, has said he plans to develop a plan to address violent extremism "in the broadest sense" and speed up the fight against not only ISIS in Iraq and Syria but other groups, like Al Qaeda, as well.

In other places in Iraq, the specter of ISIS has reappeared, as members of the group seep back into areas it once controlled, abetted by weak institutions and corrupt security forces.

REUTERS/Zohra Bensemra

Iraqi security forces members pose with a seized ISIS flag after driving its militants out of Mosul's airport, southwest Mosul, Iraq, February 23, 2017.

Clandestine ISIS members are not the only lingering threat. During the bombing campaign of the 2003 US invasion of Iraq, US aircraft deployed at least 116,000 kilograms of radioactive depleted-uranium ammunition. Logs released in 2013 showed that DU ammunition was used against cars, trucks, and many buildings.

Since then, cancer-related illness has been common in the country, particularly in Fallujah, where the rate of children born with birth defects and the incidence of radiation-related illness was much higher than in Hiroshima and Nagasaki after 1945.

"The depleted uranium left by the US bombing campaign has turned Iraq into a cancer-infested country," artist Nuha al-Radi wrote before she died of leukemia.

And according to a report this month by Airwars and Foreign Policy, the US military used depleted-uranium ammunition in airstrikes on oil trucks in ISIS-controlled areas in Syria in late 2015.