Who is Sergeant Octavio Cortez from The Forever War and what is their importance?

Sergeant Octavio Cortez is the first sergeant on Mandella's first campaign as a private. Cortez has obviously been wounded in battle, judging by the deformities of his face and head. He is the most direct authority that brings Mandella through his second campaign, when he is promoted to a Sergeant himself. Specifically, Cortez leads the very first attack on Taurans in human history, which is a bloody slaughter fought by soldiers under post-suggestive hypnosis.