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.
Lieutenant colonel (United States) In the United States Army, U.S. Marine Corps, and U.S. Air Force, a lieutenant colonel is a field grade military officer rank just above the rank of major and just below the rank of colonel. It is equivalent to the naval rank of commander in the other uniformed services.