O'Neil was an officer in the UNSC Navy.[1] He was the Chief Medical Officer aboard the UNSC Spirit of Fire.

After the Battle of Shield 0459, O'Neil suggested that all infected corpses should be burned, a suggestion that was not well-received by the rest of the crew. Despite this, the corpses were burned. O'Neil made note of this in his log.[2] O'Neil and other medical officials mistook the Flood infection as a virus, and not a parasitic lifeform.[2]


  1. Halo Wars
  2. 2.0 2.1 Halo Wars - Timeline