CIA agent (OKB Zero)

During the Soviet-Afghan war, a CIA informant was planted within the Soviet ranks at OKB Zero, and spent his time feeding information on the Soviets to his handlers at Langley. However, after uncovering information about XOF's plans to use the vocal cord parasites, and presumably XOF's former ties to the CIA, he had gone into hiding among the Mujahideen, having become paranoid that his handlers are going to kill him for knowing too much (unaware that XOF's plans were actually independent of the CIA). After the death of XOF's commander, Skull Face, OKB Zero was retaken by the Soviet forces, with the informant being suspected of having returned to the base.

Around this time, the CIA had hired Diamond Dogs to retrieve the informant. Although the PF subcommander Benedict "Kazuhira" Miller was personally against having the informant on Mother Base due to his trade, he nonetheless wanted to recruit him instead of actually giving him to the CIA, since he knew about the vocal cord parasites and ensure that neither the Soviets nor the Americans learned about the parasites existence, especially when he suspected the CIA was planning to interrogate him on the parasites.

Behind the scenes
The CIA informant was a key character in Mission 32: To Know Too Much, where the player is required to extract him.