From an early age he was trained to be a soldier and earned several nicknames due to his skill in combat. Sometime after this, he was outfitted with a cyborg exoskeleton to keep him alive after torturous experiments by the Patriots in which they removed his spine and part of his head. He was a child soldier without a documented past, absent from the databases of the NSA, CIA and FBI. In the 1990s, Raiden fought in the Liberian Civil War under Solidus Snake as a killing machine, known alternately as the "White Devil" and "Jack the Ripper",due to his incredibly high kill rate compared to other boys his age. Armed with a gun at the age of six (he would later remember it as an AK rifle), he proved to be a superior soldier, rising to become captain of the Small Boy Unit at ten. Raiden has an immense amount of nanomachines in his cerebral cortex to have him act as a back-up system in case something happened to one of the AIs. He still currently supresses the memories of his childhood, this has caused him to become depressed, silent and moody. (From the Metal Gear Wiki)