The ORION program was relaunched in the 25th century due to growing unrest in the Outer Colonies. While effective against Insurrectionists, when the CMA was essentially absorbed into the UNSC, the ORION Project was deactivated. It's augmentations made them more effective than the normal soldier, but weren't severe enough to make them stand out. The SPARTAN-II program was launched in light of the Carver Findings, and was undertaken with extreme severity to combat the coming bloodshed with ruthless precision. The SPARTAN-III program was launched out of the necessity for more Spartans to combat the increasingly devastating Covenant. Cheaper to produce, and created in larger numbers than the SPARTAN-II's, the SPARTAN-III's were utilized in a fire and forget manner against the most critical and dangerous of targets; essentially suicide soldiers. The SPARTAN-IV program was launched to replenish the Spartan ranks in order to deal with the inevitable conflict and instability that would come out of the post-war era. It was also done in a manner similar to the ORION program to avoid moral backlash.