Despite the Sentinels’ legacy as a threat to all mutants, they actually have quite a tangled history with the Hellfire Club, and in particular Sebastian Shaw, in the perpetual hope the horror of the Sentinel Program could be used to crush his foes in the X-Men, but spare him and his cohorts in the process. After Lang’s failures the vastly wealthy Shaw manipulated Senator Robert Kelley—who, after nearly being assassinated by the Brotherhood of Evil Mutants for his campaigning on anti-mutant policies, became a special liason to the U.S. government’s “Project Wideawake,” the Federal response to the emergence of mutants—into recommissioning the Sentinel program.
Unaware that Shaw himself was a mutant (they do that a lot), the U.S. government funded Shaw Industries in the development of three generations of Sentinel—the MK IV, V, and VI. The major differentiators here were mostly in their weapon loadouts, as Shaw largely used these generations of Sentinel for his own revenge, rather than on behalf of Project Wideawake—and like Lang’s work before him, none of these Sentinels were as advanced as the generations made by the Trask family. The biggest difference came in the MK V, which traded out the now-iconic Sentinel color scheme for a cool blue and grey scheme, as well as an updated body frame, but by the MK VI this had reverted.