After three months of combat in Syria supporting the assault on Raqqa, a Marine Corps 155mm artillery battery is declaring victory and returning to the states.

Officials with Combined Joint Task Force-Operation Inherent Resolve, which oversees the joint fight against ISIS, said the departure of the roughly 400 troops from 1st Battalion, 10th Marines was an indicator of the success they and coalition forces have seen on the battlefield.

"With the city liberated and ISIS on the run, the unit has been ordered home," officials said in an announcement Thursday morning. "It's replacements have been called off."

Raqqa, in Northern Syria, is the self-identified capital city for ISIS. As of this summer, it was the only Syrian city and population hub that remained under the control of the military group. A concentrated siege on Raqqa by U.S.-backed forces began June 6; Raqqa was publicly declared liberated Oct. 20. According to task force officials, some 2,500 ISIS fighters were believed to be inside Raqqa when the fight began.

For the entirety of that fight, Marine artillery units armed with M777 howitzers have been on the ground providing supporting fire. A detachment from the deployed 11th Marine Expeditionary Unit arrived on the ground in early 2017, and was replaced by 1st Battalion, 10th Marines, in mid-September.

"With a 155mm artillery battery in the fight, their mission was to deny and disrupt ISIS from gaining ground or moving from their defensive positions," Lt. Col. Jon O'Gorman, chief of fires for Combined Joint Task Force-Operation Inherent Resolve, said in a statement. "These Marines rained relentless and highly accurate firepower on the enemy."

The current detachment of Marines has earned special accolades for its grit and effectiveness.

Earlier this month, the commanding general of 2nd Marine Division, Maj. Gen. John Love, said the 1/10 battery had "killed more ISIS than anyone" with strategic fires and coordination with air assets.

Army Sgt. Maj. John Troxell, senior enlisted adviser to the Chairman of the Joint Chiefs of Staff, told reporters the unit had fired so many artillery rounds in the fight that it had burned out two howitzer barrels.

The announcement that Marine artillery will now be pulled out of the region and not be replaced is somewhat unexpected; Love told Military.com this month that 1/10 was set to be part of a long-term rotation that would maintain artillery presence in the ISIS fight.

"The departure of these outstanding Marines is a sign of real progress in the region," CJTF-OIR director of operations, Brig. Gen. Jonathan Braga, said in a statement. "We're drawing down combat forces where it makes sense, but still continuing our efforts to help Syrian and Iraqi partners maintain security.

Braga added that forces remaining in country would continue to work with local partner forces to prevent a resurgence of ISIS militants, defeat remaining pockets of ISIS presence, and enable international governments and non-government organizations to come in and help civilians recover.