Lieutenant commander

Lieutenant Commander is a junior commissioned officer rank of the UNSC Navy, equal to the rank of Major in the UNSC Marine Corps and the UNSC Army.

So far, Lieutenant Commander is the highest rank held by a Spartan-II in the case of Kurt-051 and Fhajad-084.

To some people, Lieutenant Commander may seem like the go-between rank of Lieutenant and Commander, but is actually a subclass of Commander, and a fairly high rank. In informal settings, Lieutenant Commanders are simply referred to as "Commander".