The United States Army is the oldest branch of the U.S. armed forces. Adhering to military traditions dating back to ancient Rome and earlier, the U.S. Army relies on the leadership skills of both commissioned and noncommissioned officers to accomplish its mission. The primary difference between the two is that noncommissioned officers are enlisted personnel, while commissioned officers have command authority.
Noncommissioned officers are enlisted personnel. These soldiers enlist in the Army, typically as private soldiers. Through an advancement process that includes time in service combined with additional training and experience, a private soldier may be promoted to the position of a noncommissioned officer such as corporals and sergeants. Commissioned officers, ranging from second lieutenant to general, are appointed by the U.S. president and commissioned to their role by an act of Congress. To become a commissioned officer, most candidates either go through college ROTC programs, enter Officer Candidate School after earning a bachelor's degree, graduate from the U.S. Military Academy or receive direct commissions in professional fields such as law, medicine or religion.
Commissioned officers have command authority. They are responsible for setting policy and standards, and conveying those policies and standards to the noncommissioned officers who serve under them. They are primarily involved with accomplishing the mission at the unit level. Noncommissioned officers are responsible for seeing that the policies and standards set by their commanders are carried out by the soldiers who serve in the unit. They are more involved with leading individual soldiers to accomplish the necessary tasks.
There are differences in the amount of authority given to commissioned officers and NCOs. For example, a commissioned officer might command a company of soldiers, while a noncommissioned officer might lead a platoon of soldiers. While authority can be delegated, accountability cannot. Each soldier is accountable for his or her own actions and must adhere to the rules established by the Army.
The lowest ranking commissioned officer, second lieutenant, technically out-ranks the highest ranking noncommissioned officer, sergeant major. Commissioned officers tend to be more highly compensated than noncommissioned officers even with the same amount of time in service.