>>720140872
Big Boss was a half Japanese half American from Hawaii that was sent to an internment camp during WW2 before he joined the Army and fought in Europe. Because of facing racism for his japanese heritage during the war, this made him bitter and he quit the Army soon after the war ended and became a mercenary who fought in the Congo Crises and in the Vietnam War as a MACV-SOG expert consultant. After that, he became a world famous mercenary who had his own sort of liberation ideology before he finally landed a gig running the US Foxhound group

This was the actual canon lore as laid out in official MGS material before the sequel series had Kojima basically recon all of this. He didnt lose his eye until he was much older during some random mercenary mission too in the original lore.