Commissioned officers are distinguished from other officers by their commission, which is the formal written authority, issued in the name of the President of the United States, that confers the rank and authority of a Marine Officer. Commissioned officers carry the "special trust and confidence" of the President of the United States. Commissioned officer ranks are further subdivided into general officers, field-grade officers, and company-grade officers. The highest billets in the Marine Corps, the Commandant of the Marine Corps and the Assistant Commandant of the Marine Corps are, by statute, four-star ranks, as the Marine Corps is a separate naval service under the Department of the Navy.