The All Terrain Armored Transport (AT-AT) walker, also known as the Imperial Walker, was a major part of the Axis. It was one of the most heavily armored land vehicles in the Imperial Army, but was also known for its relatively slow speed.
- "Lookit 'em, boss! Great, big, fat gray targets!"
"I know, Adam, but they've got a long reach."
- ―BJ Blazkowicz and Adam Walker, during the Great Battle of Hoth[src]
The AT-AT walker was a behemoth of a war machine, standing at a height of 22.5 meters. The quadrupedal walker closely resembled ancient beasts of war, or even a giant legendary beast from the dark side of the Force. Designed for the dual purpose of crushing and demoralizing enemy forces, and also serving as a transport for Imperial troops and light vehicles, the AT-AT was among the most awesome vehicles in the Imperial Army inventory. Its intimidating and powerful presence often earned it the distinction of being the first vehicle into a combat zone.
Serving as the "head" of the mechanical walker was a movable command section containing the command cockpit, with room for the commander, pilot, and gunner. The command section housed all of the AT-AT's weapon systems, as well as holographic targeting systems allowing the gunners a 360-degree view of their position. The cockpit was also equipped with a holoprojector for purposes of external communication. Forward visualization was supplied by a glowing red command viewport. The head could rotate as much as ninety degrees right or left and thirty degrees up or down for an expansive field of fire. Positioned above and below the command section was the walker's sensor array and blaster cannon energizer, respectively.
The command head was attached to the trapezoidal armed body section by a flexible armored tunnel, allowing cockpit access from the rest of the machine. The AT-AT's troop section could typically carry five speeder bikes, up to forty troops normally comprising Imperial stormtroopers or Imperial land assault troopers in a double-tiered passenger section, and heavy weaponry, such as E-Web heavy repeating blasters. The AT-AT could also variably hold two All Terrain Scout Transports in lieu of soldiers in a rear vehicle bay, though they required partial disassembly to fit inside. Housing the troop section were two large side panels; each one held an escape hatch. The rear panel also housed the troop staging area. Positioned in the center of the body section was a rectangular boarding hatch with sliding ramps where the AT-AT's complement of troops loaded and disembarked. An AT-AT unloaded its troops by kneeling to three meters above ground level until the boarding ramp could extend outward. Individual stormtroopers could also be deployed rapidly by rappelling cable.
Below the troop body section were two immense Kuat Drive Yards FW62 compact fusion drive systems that, in conjunction with the walker's four giant heavily-reinforced legs, propelled the AT-AT forward at a top speed of sixty kilometers per hour. However, this maximum rate was achievable only on a flat, stable terrain. At the rear of the drive motors were the walker's three fuel slug tanks, connected to the drive motors, that powered the massive machine. The AT-AT's rear also included atmospheric exchangers and a filtration unit to regulate the interior living conditions. The walker's legs were supported by massive durasteel footpads with impulse terrain sensors, supplemented each by toe flaps, that could crush obstacles in its path with little effort, effectively helping the AT-AT to live up to its name. The legs did, however, require constant maintenance and repair. As the titanic walker marched down the battlefield, its heavy, stomping feet would cause the ground to shake, demoralizing the enemy before they were even engaged.
The AT-AT's formidable offensive capabilities were supplied by dual, chin-mounted Taim & Bak MS-1 fire-linked heavy laser cannons for slower, more cumbersome targets and two fire-linked medium repeating blasters mounted on each side of the head designed for lighter, agile targets. The two sets of weapons could be independently rotated in order to engage multiple targets at once. However, the AT-AT head, which could move between a range of left, center, and right firing arcs, could only rotate one fire arc per heavy laser volley. The walker's strong external 9095-T8511 grade durasteel armor was virtually impervious to all but the heaviest of artillery weapons.
The most vulnerable part of the walker was a weak point found at its flexible neck, which was susceptible to lighter blaster barrages. The legs were also somewhat unstable and could be tripped due to a high center of gravity, leaving the walker defenseless. While first appearing to be a slow, lumbering vehicle, the AT-AT would often times be on top of its enemies before they knew what had hit them. The AT-AT also lacked armor covering on its underbelly, leaving the spot vulnerable to mounted guns or portable missile launchers. To remedy this weakness, AT-STs were usually stationed around the flank of the walker to ensure nothing was given a clear shot at the AT-AT's weak underside.
AT-ATs were typically deployed for ground assault from orbit by large dropships. Walkers stationed within larger warships, such as the Executor-class Star Dreadnought, were delivered to planetary surfaces within Incom Y-85 Titan dropships, capable of carrying four 22.5-meter AT-ATs. Smaller starships, such as the Imperial-class Star Destroyer, deployed single walkers via the Theta-class AT-AT barge. Other designs, including the Telgorn Corporation Warlord Dropship, were capable of delivering a platoon of four walkers.