What command doesn't have a command master chief?

In the Halo series, Master Chief, also known as John-117, primarily serves under the United Nations Space Command (UNSC) and is part of the Spartan program. He does not hold a command in the traditional sense, as he often operates independently or under the direction of higher-ranking officers like Captain Jacob Keyes or Commander Miranda Keyes. Therefore, he doesn't have a command in the sense of leading a division or battalion, but rather functions as a lone operative executing missions and directives.