In 1964, Big Boss (who was still known by his real name, Jack, at the time), took part in the Virtuous Mission as a member of the CIA's FOX unit. His was to rescue defecting Soviet scientist, Nikolai Stephanovich Sokolov, but unfortunately failed due to the defection of The Boss. As a result, he was imprisoned by the U.S. Government while recuperating in intensive care.
Well, I just had to rewrite this to cover up my mistake, right? Thanks to Syaza for the contribution, as well as Anon and Lane Butler for correcting me!