The All Terrain Scout Transport (AT-ST), also designated as a Scout Transport or Scout Walker, and frequently called a chicken walker, represented a lightly armored, bipedal walker deployed by the Galactic Empire's ground forces. An updated variant of the AT-ST was later adopted by the First Order for use within their military.
The AT-ST, short for All Terrain Scout Transport, served as a light walker for scouting and reconnaissance within the Galactic Empire's All-terrain vehicle series. It was composed of an armored command and control module situated atop two gyro-stabilized legs. Its functions included providing support on the battle line, hunting enemy personnel, and aiding friendly troops. They were also commonly deployed to protect the sides of larger assault walkers during major ground offensives, offering support to heavier walkers like AT-ATs by suppressing pockets of resistance and clearing out difficult terrain such as small canyons and cities located along the intended invasion path.
The command module incorporated two armored viewports designed to evoke an unsettling feeling of staring into the face of a heartless creature or an oversized combat droid, even though they were not strictly necessary due to the AT-ST's comprehensive sensor array. Within the control module, the command center featured several holoprojectors that projected a holographic 360-degree view of the battlefield. The module (or "head") itself possessed the ability to rotate 240 degrees horizontally, significantly enhancing the gunner's ability to acquire targets and inflict damage. A cooling apparatus was installed above the command module, positioned behind the entry hatch.
AT-STs came equipped with a pair of chin-mounted MS-4 twin blaster cannons that had an effective range of two kilometers. They also featured one 88i twin light blaster cannon mounted on the cheek and a DW-3 concussion grenade launcher, also cheek-mounted, which could inflict significant damage on enemy vehicles and ground forces at close quarters. The grenade launcher was particularly useful for engaging large formations of infantry and fortified emplacements that were too risky to target with rocket launchers. AT-STs also had retractable blades on their footpads, allowing them to sever wires and fences at ground level. The All Terrain Scout Transport's modular design facilitated easy customization, allowing for the addition of specific armaments and tools tailored to particular mission requirements, including mortar launchers that could be affixed to the command pod of the AT-ST.
Several sections of the walker's hull were strengthened with armored plating, notably the rear of the command module, which housed the weapon power converters, as well as the front (or "face"), the joints, and the gyro-stabilizing system. Furthermore, reinforced armor plates encased the control module, providing protection for the two-person crew against small-arms fire, but not against laser cannons, missiles, or other forms of heavy weaponry.
Due to its relatively compact size, the AT-ST could not accommodate a full onboard power generator. Consequently, it relied on eight expendable high-intensity power cells directly connected to its drive engine. An additional two cells powered the cabin gyro for backup. While these power cells met the walker's substantial energy demands, they also significantly limited its operational range.
The walker's seemingly unstable movement concealed its effectiveness as a patrol vehicle. A complex system of gyros and flexible joints maintained balance and stability across various terrains. Advanced shock absorbers integrated into the lower legs of the walker ensured constant stability, while a range of sensors within its footpads provided detailed feedback on the terrain, measuring intensity and contour for precise foot placement. The locomotion computer located in the command module could assume control of the walker, utilizing the sensor data to navigate autonomously over even surfaces, although an experienced pilot was still necessary for navigating complex terrain.
Despite its speed and agility, the AT-ST walker's offensive and defensive capabilities were notably limited. Its weapons systems were only effective against lightly armored targets at close range. Its lighter armor could withstand small-arms fire, but not laser cannons, missiles, or other heavy ordnance. The armor did not cover the entirety of its frame, to preserve its agility. Targeting the unprotected gyros beneath the command module could destabilize the walker, causing it to topple. Moreover, deep trenches or cable lines positioned at the height of the AT-ST's ankles and knees could cause it to trip and overturn. AT-STs also had a reputation for requiring frequent maintenance, potentially having the highest maintenance-per-hour ratio in the entire Imperial Army.
The Ewoks of Endor discovered that AT-STs were susceptible to anti-Gorax traps. Falling logs could penetrate the walker's head, destroying the cockpit. Another vulnerability was its susceptibility to hijacking, despite the vehicle's height seemingly rendering hijacking impossible. A sufficiently powerful force could forcibly remove the entrance hatch on top of the walker. Once commandeered, the walker's cannons could easily breach the armor of other AT-STs.
The All Terrain Construction Transport was employed for construction purposes.
The All Terrain Exploration Transport, also referred to as the "Strider," was a scaled-down version of the AT-EST Exploration and Survey Walker.
The All Terrain Scout Transport/Assault represented a direct assault variant of the AT-ST.
The AT-ST Mark IIIs were outfitted with experimental armor that provided enhanced speed and durability compared to the standard AT-ST. Armed with twin heavy laser cannons and crewed by experienced personnel, they excelled against most targets.
A variant in use by a Klatooinian tribe.
The enhanced AT-ST Walkers featured improved power couplings and subsystems, enabling their weapons to fire more powerful blasts at an accelerated rate. They also sported dark armor plating.
The All Terrain Heavy Scout represented a highly evolved iteration of the First Order AT-ST, serving in the First Order Army during the intergalactic First Order-Resistance War.
As a member of the All-Terrain walker line, the AT-ST offered improved capabilities compared to the Republic AT-RT and was operational by the time of the Invasion of Mon Cala in 18 BBY. The components for the walker's feet were manufactured by inmates at the Jubilar penal work camp.
In 14 BBY, an AT-ST launched an assault on the Stinger Mantis on Zeffo, but was destroyed by Jedi Padawan Cal Kestis. The Empire deployed AT-STs against the Partisans led by Saw Gerrera on Kashyyyk and Kestis, who aided the rebel group during their efforts to seize an Imperial refinery. AT-STs were present on Ilum when the Empire commenced mining operations to extract Kyber crystals. When Kestis journeyed to the planet in search of a crystal to construct a new lightsaber, two AT-STs were destroyed by the Padawan as he escaped the world.
The Imperial Military frequently utilized the AT-ST across a range of operational theaters. Following rebel leader Saw Gerrera and his Partisans' decision to defend Jedha, AT-STs were dispatched as reinforcements to support the planet's occupying garrison. With the ancient Holy City engulfed in surface warfare, the AT-STs were deployed for urban pacification operations against the Partisans in the city's intricate and confined streets. Despite being somewhat impractical during the Jedha insurgency, the walkers were also used to project a message beyond the reach of their blaster fire, but the Partisans instead opted to intensify their resistance against the garrison. The Empire responded in kind, and the fighting continued in the streets, with AT-STs devastating the city and its civilian population. Nevertheless, both sides persisted in their conflict, with one AT-ST deployed in Tythoni Square as part of the battle on Jedha in 1 BBY. The insurgency concluded when all but at least three percent of the Imperial garrison retreated under Protocol 13. Subsequently, the DS-1 Death Star Mobile Battle Station destroyed the Holy City.
The walkers also saw action in the Galactic Civil War. At least one participated in the Battle of Allst Prime. General Weiss commanded a customized AT-ST. Between the Battle of Yavin and the Battle of Hoth, the Alliance to Restore the Republic operated captured AT-STs, providing them to Saponza's Gang, who frequently engaged the walkers in combat. Three AT-STs were deployed as part of Lieutenant-Inspector Magna Tolvan's attack on the Son-tuul Pride crime syndicate. Several fought alongside All Terrain Armored Transports (AT-ATs) at the Battle of Hoth. They also played a significant role in the Battle of Endor, where they were defeated by the Ewoks and their anti-Gorax traps. One walker, Tempest Scout 2, was seized by the rebel Wookiee Chewbacca and two Ewoks, Widdle Warrick and Wunka.
AT-STs were manufactured at a weapons depot maintained by the Empire on the planet Sullust, which remained operational despite the planet's liberation. Infiltrating and destroying the factory, New Republic General Landonis Balthazar Calrissian and soldier Shriv Suurgav escaped in an AT-ST. The destruction of the factory deprived the Empire of additional equipment it was expecting on the planet Jakku. Nevertheless, a number of AT-STs still in the Empire's inventory were deployed in the ensuing final battle of the Galactic Civil War, the Battle of Jakku, which resulted in a decisive victory for the New Republic. In 9 ABY, an AT-ST was used by looters to attack a village on the planet Sorgan. The AT-ST became involved in the battle between the looters and the villagers, who were then led by Mandalorian bounty hunter Din Djarin and former rebel shock trooper Cara Dune. Ultimately, Djarin destroyed the walker with a grav charge.
Three decades after the end of the Galactic Civil War, a splinter military faction of the New Republic known as the Resistance utilized old Imperial AT-STs in combat against the reorganized remnants of the Galactic Empire, the First Order. They featured an orange repaint and were adorned with the Resistance starbird.
All Terrain Scout Transports made their debut in the 1980 film Star Wars: Episode V The Empire Strikes Back. The AT-ST model underwent some cosmetic alterations for its extensive appearance in the 1983 film Star Wars: Episode VI Return of the Jedi, accounting for the minor differences observed in the models used across the two films.