AT-AT

Walkers are vehicles from the Star Wars universe that traverse the landscape on mechanical legs. They are used by the Old Republic and the Galactic Empire for ground assault or transport. Throughout the saga, walkers have played a pivotal role in the fate of characters and the outcome of battles. Industrial Light and Magic (ILM) is responsible for their animation and design, often using models, stop-motion animation, and relevant matte paintings to depict their presence in the films.

There are a variety of walkers: The Empire Strikes Back introduces the All Terrain Armored Transport (AT-AT) and All Terrain Scout Transport (AT-ST). The Prequel Trilogy, Star Wars: Episode II – Attack of the Clones and Star Wars: Episode III – Revenge of the Sith introduced earlier models of walkers, such as the AT-TE, and the Star Wars expanded universe features numerous others. Walker variants have been merchandised and featured in popular culture.

The All Terrain Armored Transport, or AT-AT walker, is a giant quadruped mechanized infantry combat vehicle used by the Imperial ground forces. Standing over 20 meters tall with blast-impervious armour plating, these massive constructs are used as much for psychological effect as they are for tactical advantage.

The AT-AT (canonically pronounced "att-att" but often pronounced as an initialism) was first introduced in The Empire Strikes Back and also appears in Return of the Jedi. The AT-AT also appears in a destroyed form in Star Wars: The Force Awakens.

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Wikipedia