Successor Project

The Successor Project was a project started by the CIA at an unknown time (most likely after the events of Operation Snake Eater). The goal of the project was to produce the "ultimate field commander" using The Boss as a model. The end result produced FOX mercanary Gene, who believed he was the "successor" and Big Boss was the only other person who could rival Gene's superhuman abilities. However, the project ended in failure when Gene lost to Big Boss in their final fight to the death.

Trivia

 * The Successor Project is a precursor to the Gemone Soldiers and Les Enfants Terribles.
 * It's possible that The Boss didn't know about the Successor Project as she never mentioned it in Metal Gear Solid 3.