Dr. Nikolai Stepanovich Sokolov (Russian: Николай Степанович Соколов) was a Russian rocket scientist who defected to the United States during the height of the Cold War. Sokolov was the director of the OKB-754 Design Bureau prior to defecting, and was responsible for the development of the nuclear-armed Shagohod tank. He later developed the Intercontinental Ballistic Metal Gear, using designs from fellow scientist Aleksandr Leonovitch Granin.

Sokolov was born sometime during the mid 1900s to early 1910s. In 1960, Sokolov participated in the Soviet Vostok program, designing the multi-engine cluster for the Vostok A-1 that sent Soviet cosmonaut Yuri Gagarin to space on April 12, 1961. He wanted to keep investigating for the Soviet space program but, instead, he was named the Chief Designer of the Secret Weapons Research Office for the Soviet Union. Because of this, he also entered an intense rivalry with fellow weapons developer Aleksandr Leonovitch Granin, although he was largely oblivious to the latter's hostility to him. In 1961, he began designing the Shagohod and its intermediate range nuclear weapons capabilities. However, he began to get scared of his own creations, worrying about the weapon he was developing and its consequences on the world, and thus decided to defect from the Soviet Union with his family.

In 1962, Major Zero organized a CIA operation to help Sokolov and his family defect to the United States. Sokolov's wife and child were successfully evacuated first, with Sokolov himself following separately afterwards. However, the two-week period of travel and the 500 mile distance to get him to West Berlin exhausted him, resulting in him being checked into a local hospital to recover. Unfortunately for Sokolov, the Cuban Missile Crisis occurred one week later. On October 28, America and the Soviet Union reached a compromise: the Soviet Union agreed to remove its missiles from Cuba, but in exchange the Americans had to surrender Sokolov over to the Russians.

Sokolov returned to OKB-754 and was forced to continue his work.