He was a war hero and veteran of the water wars and the oil wars.
After the apocalypse, he got himself a nice biker gang, with his fellow soldiers as lieutenants, the bullet farmer back then was Major Kalashnikov, and the dude with the metal nose from gas town, they started going around killing other gangs, increasing their ranks until someone told them about the citadel, who was occupied by I don't remember who, another gang, they went there and besieged the citadel for a while, they made an incursion, days later Joe came out victorious, his victory in the citadel earned him the nick name "Immortan".
I hope I put that eloquently enough
Cool, thanks! I guess its more or less what I expected.