Joseph was abducted and conscripted into the SPARTAN-II program by Dr. Catherine Halsey in 2517 when he was just six years old. He was then taken to the planet Reach, and trained by the AI Déjà and Chief Petty Officer Mendez, along with the rest of the Spartan children. In 2525, he and the other candidates underwent a series of augmentations to improve their abilities. Joseph was among the ones that survived and were not crippled or killed by the procedure.
A few weeks after the augmentation procedures, Joseph along with Daisy-023 and Ralph-303 and two other Spartans rebelled against their trainers, holding them at gunpoint in front of Dr. Halsey in order to let them leave. Halsey granted them freedom, and they escaped the training facility, hoping to return home to their parents. Joseph however, was caught by the UNSC shortly after their escape.