[u]ORION[/u] - Took volunteers and gave them relatively trivial augmentations compared to the later programs. [u]SPARTAN-II[/u] - Members were conscripted at the age of six and indoctrinated. Upon reaching the age of 14 were augmented with highly invasive surgery that maimed or killed roughly half of the conscripts. The results though were extraordinary, and beyond what was expected. [u]SPARTAN-III[/u] - Orphaned children from the ages of 4 to 7 were manipulated to join with the promise of revenge against those who killed their families. They received augmentations roughly at the age of 12. They were non-invasive and chemically induced. Survival rate was 100%. [u]SPARTAN-IV[/u] - Members are chosen on a volunteer basis. Age doesn't matter as long as their genetics allow for augmentations. Augmentations involve entire organ replacements as well as an induced second puberty for enhanced growth.