Weapon X was a metahuman research initiative proposed by Dr. Truett Hudson and the mutant Nathaniel Essex in the 1970s, a spinoff of the Weapon Plus program developed under the Department of Extranormal Affairs. Weapon X suggested taking the research conducted by Weapon Plus and CADMUS and applying it to individuals who were not otherwise compliant or willing to volunteer. A covert agreement with Canada's Department K allowed the US Government to operate an otherwise illegal research facility outside of US soil.
Former Weapon Plus research subjects were kidnapped against their will and experimented upon. In 1979, Logan Howlett was kidnapped and his bones forcibly fused with adamantium. Not only was Weapon X able to refine their adamantium-bonding process, they identified the genetic sequence for rapid healing. These techniques were applied to a number of other subjects, including Yuriko Oyama and Victor Creed. Some Weapon X assets were picked up by the DEO and assigned to the black bag group called Task Force: X (Suicide Squad). Others were recovered, rehabilitated, and transferred into Stormwatch. After Howlett's escape, a young major named William Striker successfully led a coup d'etat and outed Milbury's identity as Nathaniel Essex. Striker was put in charge of what was now an illegal military facility, and Essex was forced to flee. He started several secondary projects, including the infamous Hospice.
The primary Weapon X facility was destroyed in 2011 by the First Class of Xavier's Graduates.