The mastermind behind the SPARTAN II project, Dr. Catherine Halsey, an ONI research scientist operating out of the ONI CASTLE research facility on Reach, was assigned by top UNSC brass to create a special-ops super-soldier for the defense of Earth and its colonies, as well as the preservation of the UNSC. Keeping in mind the genetic alteration and psychological demands that her work required, Dr. Halsey proceeded to hand-pick candidates for her SPARTAN II project. Although she promised herself to not grow attached to any of her 'candidates' she has always had a special place in her heart for John, SPARTAN 117. Shortly before the fall of Reach, Dr. Halsey created the artificial intelligence Cortana for use in conjunction with ONI missions, specifically for use with SPARTAN II's. Due to Dr. Halsey using her own neuro-pathways as a basis for her construction, Cortana displays the same attraction towards John, without professional or military inhibition. During the fall of Reach, Dr. Halsey and a few surviving SPARTAN II's manage to escape the planet, and eventually make their way to the classified planet of Onyx, where their current locations are unknown.