In 1995, when FOXHOUND was commissioned by the U.S. to infiltrate Outer Heaven and destroy Metal Gear, Big Boss first sent in his most trusted soldier, Gray Fox; once Gray Fox was captured, Big Boss sent in Solid Snake, at that time FOXHOUND's least experienced member. Big Boss figured that there was no way that a rookie like Solid Snake could fulfill such a mission, that his efforts would delay further action by the West and buy Big Boss enough time to complete Metal Gear's development.
However, much to Big Boss's surprise, Solid Snake succeeded in disbanding Outer Heaven, recovering the Metal Gear research data, and destroying Metal Gear itself. Faced with the failure of his plans, Big Boss confronted Solid Snake in the heart of Outer Heaven, and revealed his identity as Outer Heaven's mastermind. Big Boss laughed at the astounded Snake and told him the truth behind his mission. After Big Boss activated the base's self-destruct countdown, the two of them engaged in one-on-one combat, with Big Boss dodging between crates and firing at Snake with some kind of machine gun. Even in his advanced age, Big Boss proved fast and dangerous, but Solid Snake eventually managed to apparently kill him.
In reality, Big Boss managed to escape Outer Heaven. When NATO commenced their air raid to bomb all of the refugees and war orphans regardless of their ties to Outer Heaven or not, he also forgave the Resistance members and managed to save as many of the refugees/war orphans, Resistance Members and Outer Heaven personnel alike, as he could from the bombings, including Kyle Schneider.