The All Terrain Mobile Artillery (AT-MA) was a four-legged defense walker model utilized by the First Order for the protection of Starkiller Base. While its size and armament were similar to those of the All Terrain Armored Transport once operated by the Galactic Empire, the AT-MA's primary function was defense, not transportation or assault. To safeguard its installations, several of these walkers were stationed across the planet, with at least three present during the speech given by General Armitage Hux prior to the destruction of the Hosnian system. Within the ground vehicle storage section of a Resurgent-class Star Destroyer, multiple All Terrain Mobile Artillery walkers could be housed.
The All Terrain Mobile Artillery, initially conceived for the 2015 film Star Wars: Episode VII The Force Awakens, was first shown in a promotional image shared by Star Wars Twitter and Google+ accounts on August 10, 2015. Its identification occurred first in Star Wars: Rogue One: AT-ACT Deluxe Book and 3D Wood Model, a Star Wars IncrediBuilds woodshop activity book penned by Michael Kogge and launched on May 23, 2017.
The Art of Star Wars: The Force Awakens includes concept art for vehicles resembling these walkers.