Operation Majestic Twelve, in the Atomic Robo universe, is an effort by the U.S. Government to analyze and understand the workings of the technology left by Nikola Tesla after his death in 1943, and may be a critical plot point in the series. The operation was approved by Harry S. Truman after the Secretary of Defense, James Forrestal, convinced him that it would be greatly important in the midst of the Cold War era to do research on the technology so that they can be weaponized against the Soviets.
How this operation is linked to Robo is quite ambiguous, as Truman mentions that Robo could be a great asset to the effort, but Forrestal disagrees, as Robo's loyalty to the government and their secret plans is questionable. Robo is against the idea of containment and may have gotten in the way of Operation Paperclip.
In 1997, it is found out that Robo knows of Majestic Twelve and its motive in analyzing Tesla's technology due to some "screw ups" in the past. Upon Tesla's death in a lab explosion in 1943, the unknown organization salvaged any remaining piece of technology found in the fire without Robo's authorization. It is suffice to say that Robo was not happy with this, and vows to fight back at some point in time. He alludes to the missions and orders the military put him through in the past, and wonders if any of it involved the operation at some degree.