The All Terrain Armored Transport (AT-AT) walker, also known as the Imperial Walker, was a major part of the Galactic Empire's motor-pool. Carrying a vast amount of fire power and being heavily armored, the AT-AT was argueably the most feared and effective land vehicle in the Imperial Army, and enjoyed a long life span, from the Clone Wars to the Second Imperial Civil War, over 150 years later. However, it was also known for its relatively slow speed.
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 astonishing vehicles in the Imperial Army's inventory. Hundreds of these walkers were produced during the Galactic Civil War, and 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. An AT-AT walker deployed to the moon Yavin 8 carried a distress beacon which was launched aboard a missile.
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 flat, stable terrain. At the rear of, and connected to, the drive motors were the walker's three fuel slug tanks 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 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's 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 its flexible neck, which was susceptible to lighter blaster barrages. If punctured, it can lead to a reactor breach, although it was considered an unlikely scenario, it nonetheless was considered potentially catastrophic. The legs were also somewhat unstable and could be tripped due to a high center of gravity, leaving the walker defenseless. In addition, when tripped, AT-ATs do not regain footing easily, and they are also vulnerable to crumbling terrain. Damaging its knee joints can lead to loss of mobility, being less sound than the other parts of the leg due to their representing the flexible joining of two components, with the joints being vulnerable to artillery attacks. While first appearing to be a slow, lumbering vehicle, the AT-AT would often 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 walker's flanks to ensure nothing was given a clear shot at the AT-AT's weak underside. The walker could also be disabled with shots to the knee joint. In addition, they also lacked rear facing weaponry, and while sufficiently armored, their primary purpose nonetheless was to act as troop transports, and thus have comparatively lighter armaments compared to other mainstay walkers in the Imperial Army. In order to compensate for these glaring blind spots, the AT-ATs are often deployed in staggering formations, as well as accompanied by support vehicles.
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 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 armor platoon of four walkers.
The Empire utilized several modified variants of the standard AT-AT design for purposes of fitting certain mission profiles in specific environments. The walkers used at the Battle of Hoth in 3 ABY—nicknamed "snow walkers"—were specially designed with heat circulation systems, de-icing controls, and energy efficient environmental controls.
The AT-AT "dune walker" was a desert terrain walker fitted with Sienar Fleet Systems z23 heat dissipation units; while the Aquatic Terrain Armored Transport, known as the AT-AT "swimmer," was a repulsorcraft cousin of the standard model. There was also the All Terrain Ion Cannon, a long-range artillery gun mounted on an AT-AT chassis.
Various planetary garrisons often modified their AT-ATs to suit the local environments, with various modifications including gas filters, heat recirculators, and anti-corrosive sheens. The Aquatic Terrain Armored Transport, also known as the AT-AT Swimmer, was an extreme modification created by the Imperial Army garrison for use on Kabaira.
- "The pride of the Imperial Assault Armor Division, the quadrupedal AT-AT stands 22.5 meters and is recognized as a symbol of intense power. The AT-AT has a potent effect on primitive Rimmers who see it as a gargantuan beast, as well as galactic citizens trained by propaganda to believe the appearance of an AT-AT means all is lost."
- ―Colonel Maximilian Veers, Imperial Handbook: A Commander's Guide
Clone Wars origin and development
The first-generation AT-AT walkers saw their debut during the Battle of Jabiim, later on in the Clone Wars. During this battle, the overwhelmed Confederacy forces were annihilated by them. Their significance waned when the walkers were slowed down by the muddy surface of the planet, making it easier for the enemy units to bring them down. At some point, AT-AT walkers managed to fall into the hands of the CIS, with at least one unit being kept in a research facility on the Separatist world of Diado.
- "Will you look at those walkers? Has there ever been anything so big and gray and ugly, Luke?"
"If you don't like 'em, I'll take you down where you can do something about it, Dak."
- ―Dak Ralter and Luke Skywalker, during the Battle of Hoth.
During the time of the Galactic Empire, AT-ATs were not completely forgotten, as a later-generation model participated in the Battle of Orion IV. AT-ATs were being tested on the planet Carida when the Rebel Alliance attacked. The AT-AT was instrumental in winning the battle. After the Battle of Yavin, it was Maximilian Veers that fully resurrected the concept, bringing the AT-AT into full Imperial service. They were deployed on a wide array of worlds in the following months, including Corellia, Chandrila, and Ghorman. Largely because of it resembling a large beast in the Outer Rim and Imperial-made propaganda reinforcing its near-invincible status, civilians within both the Rimmers and various galactic civilians, with Mon Mothma also explicitly stating the Rebel Alliance refuses to use the vehicles due to their acts of psychological destabilization, since they represented hope instead of fear. Nearly three years after the Battle of Yavin, Veers neared completion on a superior model while on Zaloriis. This was nicknamed the "Dune Cow". With the prototype Blizzard 1, constructed at Camp Culroon, Veers assaulted the planet's capital when Zaloriis declared their affiliation with the Rebellion.
At least one AT-AT was used at the Battle of Boz Pity. The AT-AT was unknowingly steered into a trap set by Renegade Squadron; a detonation pack was used to blow up a hidden cache of explosives, and the huge explosion toppled the machine. However, the battle was ultimately a victory for the Empire.
Several AT-ATs were also deployed to Ralltiir to subjugate the scientists, although several of them were destroyed after Red Squadron destroyed the bridges into the city with bombs, developed by scientists, and their speeders.
At the Battle of Hoth, the Empire's Blizzard Force utilized AT-ATs to assault the Rebel's Echo Base, as it was protected from above by an energy shield. Due to their weight, and the unstable terrain they were traversing, a few were lost before the battle even began. General Maximilian Veers commanded the ground forces and advanced on the shield generator, decimating Rebel troopers in their trenches. Blizzard Force's frequent usage of AT-AT's was largely the reason behind their logo adopting an image of the AT-AT.
Faced with such forces, Luke Skywalker employed a strategy earlier devised by himself and strategist Beryl Chiffonage to disable the walkers: his squadron of snowspeeders would use their magnetic harpoons and tow cables to entangle the walkers' feet, toppling them. Wedge Antilles and his gunner, Wes Janson, managed to disable one walker using this method. Luke destroyed two more by cutting a hole in each with his lightsaber and tossing in a concussion grenade.
Dash Rendar was able to bring down a third through unknown means. Another AT-AT that closed on Echo Base was destroyed by Renegade Squadron, which used particle cannon turrets to destroy the war machine. (The dangers of AT-AT walkers toppling was discovered by an Imperial Cadet named Davin Felth, but the oversight was not corrected by Colonel Veers prior to deployment.)
Despite these small successes, they were ultimately insufficient to turn the tide of the battle, and the Battle of Hoth was one of the most devastating losses for the Rebellion in the entire Galactic Civil War. The AT-ATs succeeded in destroying the shield generator, thereby allowing the main Imperial force to land and attack Echo Base. The AT-ATs would go on to devastate the Rebel defenses.
During the Battle of Dubrillion, Wedge Antilles, after infiltrating the Dubrillion superlaser facility in an All Terrain Scout Transport, managed to hijack an AT-AT Walker inside of a hangar. Wedge then proceeded towards the generator room and used the walker's firepower to destroy the superlaser facility's turbines and destroy the facility and the superlaser for good.
Several AT-ATs also broke out of the Imperial I-class Star Destroyer Motivator after it was shot down from orbit during the Battle of Kothlis, although Rogue Squadron managed to down them in the ocean.
At least one AT-AT patrolled the garrison base on the forest moon of Endor, but had no impact on the battle there, as AT-ATs were limited in their range by the dense foliage of the moon. As a result, smaller vehicles, such as All Terrain Scout Transports, saw far more use. An AT-AT was originally going to be used in the Battle of Endor, but it was crippled by Renegade Squadron, resulting in portions of the Galactic Empire attempting to fix it.
In 5 ABY, an AT-AT was patrolling on Ruusan as the Imperial faction, led by the Seven Dark Jedi, searched for the Valley of the Jedi. Shortly after cutting down Sariss, Rebel mercenary and rising Jedi Knight Kyle Katarn headed for the Valley himself, passing through the standby AT-AT as he went.
By 9 ABY, Nomad City on Nkllon was a mining operation owned by Lando Calrissian. The city was built from a Dreadnaught-class heavy cruiser mounted on top of 40 captured AT-ATs to constantly move the city away from the day side of Nkllon and prevent it from being destroyed by the intense radiation of Nkllon's sun. However, the city was damaged and later abandoned, leading to the eventual destruction of Nomad City and its AT-ATs by the intense radiation.
During the reborn Emperor Palpatine's insurgency in a clone body from 10 ABY to 11 ABY, the Empire developed a new variant of the AT-AT that was equipped with the most powerful Imperial turbolasers and the new X-80 power cells. These were deployed during an attack on New Alderaan. During the battle, they vaporized many buildings, gun emplacements and starfighters.
During the Yuuzhan Vong War, AT-ATs were found on the Imperial Remnant planet Shramar, and battled a Yuuzhan Vong army during the battle there. The New Jedi Order's Myrkr strike team found one of these vehicles on the Yuuzhan Vong Koros-Strohna Baanu Rass in 27 ABY. AT-ATs were also deployed by the Galactic Federation of Free Alliances during the liberation of Coruscant in 29 ABY. It was the predecessor of the All Terrain Armored Heavy Transport model, but was still used by Darth Krayt's Galactic Empire in 138 ABY.
Behind the scenes
The name "AT-AT" is never spoken in any of the films. Instead, the machines are referred to as "Imperial walkers."
In the Star Wars: Episode V The Empire Strikes Back DVD commentary, George Lucas explained that he got the idea of the AT-AT from the massive tripods from H.G. Wells' 1898 novel The War of the Worlds. Joe Johnston also claimed that the inspiration for the AT-AT was in fact the Cybernetic Anthropomorphous Machine (CAM), which had been commissioned by the United States Army for potential use in the Vietnam War, before being abandoned by General Electric due to the design proving to be too exhausting to operate. It was rumored that Lucas' inspiration for the AT-AT walkers were four legged cranes at the port of Oakland, although Lucas denied such was the case.
The animators who brought the AT-AT Imperial Walkers to life in The Empire Strikes Back based their movements on elephants.
AT-ATs frequently appear in video games, though in games they vary in durability. In some games they can be damaged by shooting them, such as in Shadows of the Empire and the Battlefront series, though in the latter their durability makes using blasters impractical. In the Rogue Squadron games, AT-ATs are completely immune to all weapons and can only be destroyed with a Snowspeeder's tow cables, except for one mission where a Snowspeeder carries bombs with its tow cable that are powerful enough to destroy an AT-AT. Typically, their weapons are easy for the player to avoid, but destroying the walker can prove to be difficult because of their strong armor.
Additionally, in the gaming book Star Wars Missions 4: Destroy the Liquidator, an AT-AT can be destroyed by a choice between shooting the knee joints or using a harpoon cable, just days after the Battle of Yavin.
During development for Rebel Strike, the third entry for the Rogue Squadron video game series, the development team, because of their insistance of rebuilding the Rogue Leader game coding entirely from scratch to make it different from its predecessor, ran into some gaffes and problems during animation. One of these gaffes was Luke Skywalker's harpoon cable attaching to the AT-AT's neck, and then walking it as if it were a giant dog, during the development of the Battlefield Hoth mission.
At Disney World's Hollywood Studios, a giant model of an AT-AT is located just outside Star Tours.
In July, 2010, Hasbro released an AT-AT vehicle capable of holding up to 19 figures. Included with the vehicle is a speeder bike and one AT-AT driver.  On a translucent decal image on the cockpit's "viewscreen" is a personal note from Brian Parrish (Hasbro's Design Manager for the Star Wars franchise) that reads, "HOPE YOU ENJOY THE AT AT," on the screen above the photo image of the Rebel power generator, with "B. PARRISH" on the next line, underneath. In addition, other phrases in Aurebesh are visible on the clear acrylic screen that read, "REGULAR MODE," "INFRARED MODE," "MAX," "MIN," "ZOOM IN," and "ZOOM OUT," as well as the numbers, "077 254 72 7." 
First use discrepancy
The 2001 video game Star Wars: Galactic Battlegrounds has a mission which describes the creation of the AT-ATs and their introduction to the service of the Empire. All this happens before the Battle of Hoth. However, there are several appearances of the AT-ATs in BBY sources, including the video games games Star Wars: Rebel Assault and Star Wars: X-Wing. The first is S-canon; however, the latter is accepted as C-canon and shows them in the Battle of Orion IV. First-generation AT-AT walkers are featured in the comic story-arc Star Wars: Republic: The Battle of Jabiim. The 2006 video game Star Wars: Empire at War shows them being introduced before the Battle of Yavin. The 2011 comic book Star Wars: Darth Vader and the Lost Command shows them in use just after the Declaration of a New Order in 19 BBY.
AT-AT is pronounced "at-at" in Star Wars: Force Commander, and Star Wars: Galactic Battlegrounds. They are also called "A-T-A-T"s briefly in Star Wars: Rogue Squadron II: Rogue Leader. In Star Wars: Battlefront II both terms are used. However, in Star Wars Battlefront: Renegade Squadron, it is pronounced "A-T-A-T".
- "Outpost Beta here. I have a visual now. These things look like … animals. They're huge, maybe twenty, twenty-five meters high, four-legged, and their heads move. But they're made out of metal. They have extremely heavy armor and armament. I count six of 'em so far."
- ―BETA, in the script of the The Empire Strikes Back radio dramatization
- "Outpost Beta here. I have a visual now. These things look like … animals. They're huge, maybe ten, fifteen meters high, four-legged, and their heads move. They're made out of metal. They have extremely heavy armor and armament. I count six of 'em so far."
- ―BETA, in the recording of The Empire Strikes Back radio dramatization
In "Forces of the Empire," an article that was first published Issue 2 of The Empire Strikes Back Official Poster Monthly, the All Terrain Armored Transport was described as "a fifty-foot tall armored exoskeleton." The figure of fifty feet was likely derived from sources such as The Empire Strikes Back Sketchbook, which suggested that the designers of the model intended for the AT-AT to appear as fifty feet tall on screen. In 1984, this figure was given as the height for the AT-AT in the first edition of a A Guide to the Star Wars Universe
In 1983, The Empire Strikes Back radio dramatization included a scene in which a young Rebel officer, who would be later identified as Maren Kelsome, gave the command staff of Echo Base a rough estimate of the height of the AT-ATs approaching his location. His statement that they were "twenty, twenty-five meters high" in the script later was changed to "ten, fifteen meters high" in the recorded version.
Supplements for West End Games's Star Wars roleplaying game listed the All-Terrain Armored Transport at a height of 15.5 meters. Inside the Worlds of Star Wars Trilogy revised the AT-AT's height to 22.5 meters in a section dealing with the dropships that were used to land the walkers during the Battle of Hoth. This larger figure was based upon unofficial calculations by Curtis Saxton, with whom James Luceno, the author of the book, consulted on technical matters. It was calculated using a scene in The Empire Strikes Back where Luke Skywalker is ascending a cable beneath a walker.
This figure was repeated by Star Wars: Complete Locations, a compilation of the Inside the Worlds of series, but the "Episodes IV-VI Data Files" section of Star Wars: Complete Cross-Sections listed the AT-AT's height at 15.5 meters, adding further confusion to this issue. Yet another alternative size for the AT-AT was shown in the Hyperspace fan club kit, which included a desktop wallpaper depicting various vehicles in scale with each other. Compared to the HAVw A6 Juggernaut, which is unambiguously known to be 49.4 meters long and 30.5 meters tall, the AT-AT is shown to be 18.5 meters in height.
- LEGO Star Wars: Microfighters video game
- LEGO Star Wars II: The Original Trilogy
- LEGO Star Wars: The Complete Saga
- Star Wars Infinities: A New Hope
- Star Wars Infinities: The Empire Strikes Back
- Star Wars: The Empire Strikes Back video game
- Star Wars: The Force Unleashed video game — Ultimate Sith Edition
Notes and references