only one in four persons in the United States of the proper age meet the moral, academic and physical standards for military service. Personnel by service 2020 Demographic Reports and end strengths for reserve components. Rank structure Rank in the United States Armed Forces is split into three distinct categories: officers, warrant officers, and enlisted personnel. Officers are the leadership of the military, holding commissions from the president of the United States and confirmed to their rank by the Senate. Warrant officers hold a warrant from the secretaries of the military departments, serving as specialist in certain military technologies and capabilities. Upon promotion to chief warrant officer 2, they gain a commission from the president of the United States. Enlisted personnel constitute the majority of the armed forces, serving as specialists and tactical-level leaders until they become senior non-commissioned officers or senior petty officers. Military ranks across the services can be compared by U.S. Uniformed Services pay grade or NATO rank code. Officer corps Officers represent the top 18% of the armed forces, serving in leadership and command roles. Officers are divided into three categories: O-1 to O-3: Company grade officers in the Army, Marine Corps, Air Force, and Space Force or junior officers in the Navy. O-4 to O-6: Field grade officers in the Army, Marine Corps, Air Force, and Space Force or mid-grade officers in the Navy and Coast Guard. O-7 to O-10: General officers in the Army, Marine Corps, Air Force, and Space Force or flag officers in the Navy and Coast Guard. Officers are typically commissioned as second lieutenants or ensigns with a bachelor's degree after several years of training and education or directly commissioning from civilian life into a specific specialty, such as a medical professional, lawyer, chaplain, or cyber specialist. Officers are commissioned through the United States service academies, Reserve Officer Training Corps programs, and the Officer Candidate and Officer Training Schools. During a time of war, officers may be promoted to five-star ranks, with general of the Army, fleet admiral, and general of the Air Force the only five-star ranks currently authorized. Warrant officer corps Warrant officers are specialists, accounting for only 8% of the officer corps. Warrant officers hold warrants from their service secretary and are specialists and experts in certain military technologies or capabilities. The lowest-ranking warrant officers serve under a warrant, but they receive commissions from the president upon promotion