spartan 1 aka orion project: super soldiers who's cost far outweighed the benefits. They did not have armor and looked like normal soldiers. Johnson was a candidate in this program. Program was cancelled do to cost. Spartan II: the best produced super soldiers. They where kidnapped at six and basically brainwashed to follow orders regardless of what they are. This consists of master chief. They where forced puberty on steroids so they could grow very tall and enhanced in every possible way. They are taught nothing but war at age six, so you can imagine how use full and tactical they can be and they have a will of iron. Add that they go it mjolnir armor that boosts their strength. Spartan III: Orphans taken from all over galaxy. They resemble spartan II's in almost every regard except armor. They used spi armor which used light bending camp technology but was less protective. This spartan project was the most secretive as they massed produced Spartans to go on complete suicide missions. Almost every group created was wiped completely except for the most effective Spartans who would be more use full alive than on wasted on a suicide mission. These few consisted of headhunters and noble tram on halo reach. Spartan IV: adults who had been given the choice to join. ( not kidnapped) they are still augmented as well but since they had normal lives instead of being trained from age six, they are much more relatable. They question orders and are much LESS affective on the battlefield.these Spartans consist of Sara palmer, buck, romeo, and all the Spartans in spartan ops. My theory is chief has seen almost everyone he new killed due to the unsc using him in every regard, so after years of following blindly, he began to question their motives and went AWOL.