This is the massive cannon US Marines are using to obliterate ISIS fighters in Syria

As coalition forces slowly make gains in liberating Mosul from ISIS control, another campaign to finally oust the terror group's forces is taking place in Raqqa, Syria.

According to The Washington Post, a contingent of US Marines from the 1st Battalion, 4th Marine regiment recently established a combat outpost in Syria to assist local US-backed forces, who have begun their assault on the city.

By providing support through various means, Coalition troops have reportedly killed hundreds of enemy fighters and destroyed more than 200 fortifications. Coalition forces have also claimed that they've conducted more than 300 airstrikes around Raqqa in the past month alone.

One of the ways in which the Marines have pounded their enemies is with the fearsome M-777 Howitzer. Firing 155-millimeter shells, these cannons can have a range up to 25 miles with special GPS-guided munitions.

Here's a look at the deadly weapon that the Marines are hitting ISIS with.