Nikolai Stephanovich Sokolov is a Russian rocket scientist and elite engineer who was forced into serving Colonel Volgin during the events of Operation Snake Eater. He is a specialist in weapons technology, although he originally studied science to construct space rockets. He is the catalyst of the conflicts throughout Snake Eater.
Sokolov defected to the States secretly, however America and the Soviet Union agreed that in return for the Russians removing their missiles from Cuba, America would send Sokolov back to the Soviet Union. Rescuing Sokolov is one of Snake's primary objectives in the game. However, Snake's initial attempt to save Sokolov during the "Virtuous Mission" fails.
In "Operation: Snake Eater", Sokolov is taken to Groznyj Grad to finish the Shagohod - a weapon he was forced to create under threat of his own death. He gives the weapon data to EVA, and is later rescued by Snake. He refuses to leave, stating that no matter where he goes, he will be used to create weapons of mass destruction. He also asks Snake to watch over his family, which is in the CIA's custody. When Volgin discovers Snake, he shoot's Sokolov's knees, immobilizing him. He is later seemingly beaten to death during interrogation by Volgin.
