who is the highest ranking in the army
United States military seniority A type of "positional seniority" exists for military officers who hold top leadership positions of the armed forces. For instance, the Chairman of the Joint Chiefs of Staff is considered the senior most officer of the entire United States military, even though it is possible that contemporaries of the same rank may have earlier dates of rank or time in service. Likewise, heads of various armed service branches are considered senior most within their service; unified commanders are also considered senior most in their respective regions yet not necessarily to each other.
Sergeant Major of the Marine Corps In the U.S. Marine Corps, sergeant major is the ninth and highest enlisted rank, just above first sergeant, and equal in grade to master gunnery sergeant, although the two have different responsibilities. A sergeant major typically serves as the unit commander's senior enlisted adviser and to handle matters of discipline and morale among the enlisted Marines. The Sergeant Major of the Marine Corps is chosen by the Commandant of the Marine Corps to serve as his adviser and is the preeminent and highest ranking enlisted Marine with an order of precedence of a lieutenant general.[3]