A mass-produced mobile suit of the "New Millennium Series" developed by ZAFT to be its new mainstay machine, it is often referred to simply as "ZAKU", which is an acronym for "ZAFT Armored Keeper of Unity". The ZAKU Warrior was based on the ZAKU Mass Production Trial Type, a nuclear-powered mobile suit created by ZAFT after the First Alliance-PLANT War for mass production. However, due to the ban on military use of Neutron Jammer Cancellers placed by the Junius Treaty signed later that officially ended the war, the ZAKU Warrior is powered instead by a conventional battery system unlike its predecessor. Even so, its default capabilities exceeds those of the GAT-X series deployed by the Earth Alliance during the war, as well as the previous mainstay machines used by ZAFT.
The Junius Treaty also placed strict limits on the number of ships and mobile weapons each superpower can maintain, and to comply with the limitation, the ZAKU Warrior was designed with high operability and versatility. This was achieved through the use of the "Wizard System", a series of interchangeable armament packs usually mounted on the ZAKU Warrior's back, but other attachment locations and methods also exist.