A unique approach was used to create the film's traditional 2D animation: the actors performed every scene of the film using motion-capture technology, which was translated into 3D animation within Unreal Engine's real-time game engine; this 3D environment was used to determine the film's camera angles and movements, and this was translated into the final 2D animation.
Billy Boyd and Dominic Monaghan, who played Pippin and Merry in The Lord of the Rings trilogy, voiced the orcs Shank and Wrot in this movie.
The film is narrated by Miranda Otto as Éowyn, reprising her role from Sir Peter Jackson's "The Lord of the Rings" series.
One of the biggest challenges for the animation team was the large number of horses in the film; horses are important in Rohan culture but they are also notoriously difficult to animate.
The movie focuses on the history and backstory of Helm's Deep, the same location seen in The Lord of the Rings: The Two Towers (2002).