I read the entire Book on HALO, John was kidnapped from his parents at the age of 6 years old by the U.S Government because he showed signs of a very capable child, (strength, Intelligence, endurance) above all other children. they replaced him as a clone with his original Mom & Dad so they wouldnt notice their real son was gone. The U.S Government then started conducting experiments on John, infusing chips, super training, muscular harden enhancement and a built in AI chip called ‘Cortana’ based off of Dr Halsey, her younger self, which is why the Chief has a close connection to Dr. Halsey and Cortana being his replacement mothers. Spartan 117 accomplished many missions succesful, even stopping the annihilation of the world.. for those who don’t know, John is (Spartan 117 Master Chief) here is some new footage of HALO 6 Infinite.