When the five scientists who designed the XXXG-00W0 Wing Gundam Zero in AC 180 went their separate ways, each of them took copies of the plans for their original Gundam design. Doktor S, who went into hiding in the L3 colonies, then went on to design and build his own Gundam based on their original plans. Built with the support of the Barton Security Group, Doktor S's XXXG-01H Gundam Heavyarms was intended to be used in the originally planned Operation Meteor, which involved dropping a space colony on Earth. Doktor S and his assistants, not wanting their Gundam to be used as a tool for mass murder, killed the Heavyarms' intended pilot, Trowa Barton. One of the mobile suit's mechanics, a mysterious and nameless young man, assumed Trowa's identity and took the Heavyarms to Earth in the "new" Operation Meteor, foregoing the colony drop and instead using the Gundam directly against OZ's military forces.

In addition to being built of almost indestructible gundanium alloy, the "Gundam 03" (as it was code-named by OZ) was a virtual walking fortress, packing an enormous amount of firepower in the form of Gatling guns, machine cannons, vulcan guns, "blind" and homing missiles, and a large shield-laden beam Gatling gun. While this firepower could overwhelm a large number of enemies, the Heavyarms often paid the price by quickly running out of ammo. However, the Gundam also carried a heated "army knife" blade on its right forearm for close combat. The "new" Trowa Barton, with his fast reflexes and acrobatic abilities, would often rely on these skills to effectively keep himself (and his Gundam) alive even when he was dry on ammo... thus ensuring that the Gundam Heavyarms would never go down without a fight.