The Zaku I was already considered five years outdated by the outset of the One Year War, and was relegated mostly to out-of-combat duties such as training and patrols. However, the suit does have a notorious background, as it was used in the large-scale gassing of colonies to prepare for their drops on Earth. Although they saw action as the war drew to a close, they would never again be seen as the military masterpiece that they had been when they were first created.