Supreme Commander

Supreme Commander is a very high Covenant Elite (Sangheili) rank.

Background
For most of the Covenant's history, this rank was held by the Elite race, but was gradually mixed then replaced completely by Brutes after the Great Schism. They now command Fleets and Armadas.

Rank
Supreme Commander is the rank which commands a large Covenant Fleet, such as the Fleet of Particular Justice formerly led by Thel 'Vadamee. Lesser fleets may be commanded by Fleet Masters, a lesser rank than Supreme Commander.

Physical Appearance
When commanding a Fleet, Supreme Commanders wore Zealot gold armour with a cloak that wraps around and over the armour piece of their shoulders. In fact, the Supreme Commander's unusual helmet looks very similar to the Halo 3 Elite combat helmet when compared closely.

Appearances
The particular Supreme Commander in the aforementioned text was a friend of, and yet superior to, Rtas 'Vadumee and would later become the Arbiter. During the Civil War of the Covenant, it is possible the Brutes took these positions from the Elites. But even so, some Supreme Commanders escaped to fight the Brutes.