"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.