"Atlas Huntsmen vs. Centinels" is a series of fights that occurred in "Ace Operatives" as Team RWBY, Jaune Arc, Nora Valkyrie, Lie Ren and the Ace Operatives are ambushed by several Centinels while hunting a Geist in the abandoned Dust mine.
To prepare for the launch of Amity Colosseum, Atlas Huntsmen were sent to clear the launch site of all Grimm, however they encounter a Geist which evades destruction and kills several huntsmen. When Atlas strengthens it's force to kill the Geist, it was smart enough to flee into the abandoned dust mines, revealing it is an old Grimm, making it stronger than normal. Teams RWBY, JNR and the Ace-Ops split into three groups and enter the abandoned dust mines to hunt the Geist. The groups go as follows: Alpha consists of Clover Ebi and Qrow Branwen. Bravo consists of Team RWBY, Harriet Bree and Marrow Amin, and Charlie consists of Team JNR, Elm Ederne and Vine Zeki.
Bravo team reach a blocked section of the mines with a gap small enough to squeeze through. Being the only one small enough to fit through with night vision, Blake Belladonna goes through the gap to make sure the other side is clear off dust so the others can smash through the rubble without causing an explosion. After confirming the coast is clear, she is attacked by the Geist. Harriet smashes through the wall with her weapon while the others shoot at the Geist, causing it to flee. However the noise attracts several Centinels to their location.
Team RWBY moves to follow the Geist before a Centinel erupts from the ground. Yang punches the Grimm causing it to retreat as more begin emerging. Ruby, Blake and Weiss each attack one while the others confront more nearby. Two close in on Yang who plants explosives with a few strikes, leaping to a safe distance before detonating them.
Ruby slashes another with Crescent Rose, then rotates the blade to finish it off. She begins firing as Marrow rushes by gunning down two Centinels. He switches Fetch into boomerang form and throws it. The weapon bounces off a wall into a third Grimm, returning to Marrow as he dispatches it. Two Centinels move toward him but he freezes them with his Semblance, allowing Harriet to eliminate both.
Charlie slide down into another chamber encountering opposition. Vine and Elm uses their Semblances to slow down in preparation. But Jaune, Ren and Nora keep going as Jaune unleashes a shock-wave from his shield. With the Grimm stunned Ren uses StormFlower"s upgrade to fire the blades at one, pulling himself toward before unloading a burst of gunfire. Nora quickly eliminates the other two before they can react.
Back with Bravo there is one Centinel left, Ruby is about to open fire. Only for Harriet to run past and hit it first. Meanwhile Clover and Qrow find the Geist, but it dodges their attacks managing to slip away.