Within military organizations, the use of ranks is almost universal. The Chinese People's Liberation Army of the 1960s and 1970s and the Red Army of 1918-1935 are the rare examples of military which attempted (quite unsuccessfully) to abolish rank.
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The use of formalized ranks came into widespread use with the Roman legions after the introduction of reforms by the consul Gaius Marius which were completed around 60 BC. In the new system a legion would be commanded by a legate (legatus), typically a senator given a three-year term. Immediately beneath the legate were six tribunes of the soldiers (tribuni militum), five of whom would be senior officers and one a nobleman who was headed for the Senate.
The fighting men in the legion were formed into ranks, rows of men who fought as a unit. In the new system these were divided into groups of ten cohorts (cohors, pl. cohortes), each consisting of six centuries of 100 men. Each century was led by a centurion (centurio, pl. centuriones). Additional centurions served as scribes and filled other duties. Centuries were further broken into ten contubernia, of eight soldiers each. Individual soldiers were referred to as soldiers (miles, pl. milites) or legionaries (legionarii).
Most modern military services recognize three broad categories of serviceman. These are codified in the Geneva Conventions, which somewhat ambiguously distinguishes "officers", "non-commissioned officers" and "men".
Apart from possible conscripted personnel one can distinguish:
- Commissioned officers which are further separated into three levels
- Flag Officers — Admirals, Generals and Marshals who typically command units that are expected to operate independently for extended periods of time (brigades and larger, fleets of ships).
- Field Grade Officers who typically command units that can be expected to operate independently for short periods of time (battalions and regiments, large warships). Field Grade officers also commonly fill staff positions.
- Company Grade or Junior Officers are the three or four lowest ranks of officers. Their units are generally not expected to operate independently for any significant length of time. In the US Army and the US Marine Corps, these are captains and lower who typically lead companies and smaller units. In the US Navy, these are lieutenants and ensigns who typically command divisions or watches on larger ships. Company grade officers will also fill staff roles in some units.
- Warrant officers are a hybrid rank treated slightly differently in each service. Generally speaking, warrant officers are given the rank for technical skills and do not serve in command positions. However for Geneva Convention purposes they are usually treated as commissioned officers.
- Enlisted personnel
- Non-commissioned officers (NCOs) are enlisted personnel who supervise other soldiers or have significant administrative responsibilities. Even the most senior NCO officially ranks beneath the most junior commissioned officer, although in many organizations a senior NCO will have formal responsibility and informal respect beyond that of a junior officer. NCO ranks include a varying number of grades of Sergeant (Army, Air Force or Marines) or Petty officer (Naval).
- Other enlisted ranks include the "specialist" and the "private soldier" or private for short.
Typical Army commissioned officer ranks and responsibilities
|a/an||is typically led by a||and consists of|
|Army group||General or Field Marshal||several Armies|
|Corps||Lieutenant General||several Divisions|
|Division||Major General||several Regiments or Brigades|
|Brigade or Regiment||Brigadier General or Colonel||several Battalions|
|Battalion or Task Force||Lieutenant Colonel||several Companies|
|Battalion or Task Force||Major||Staff adjutant or Second-in-Command|
|Platoon||First or Second Lieutenant||several squads or sections|
Many of these ranks are recent additions. Many officers have no direct command function but are Staff Officers charged with strategic planning, training, intelligence, transportation, logistics, supply, pay, medical, and any of the other minutia of modern military organization.
The basic unit, that is the smallest unit capable of self-supporting operation, of an army up to about the 16th century was the Company, which was known as a Troop in the cavalry and Battery in the artillery.
Brigades and Divisions later became the basic unit, with the Brigade replacing the Regiment outright in the British Army. The Division is now the lowest regular army unit that is equipped and supplied to routinely operate independently in the field. (Armored Cavalry Regiments and Special Operations teams are the exception.)
During most of the time since the fall of the Roman Empire the head of the military forces has been the King, often leading in person. This role, if filled, has since been passed on to dedicated military officers known either as General of the Army or by a Field Marshal.
Typical Army non-commissioned officer ranks and responsibilities
|a/an||is typically led by a||and consists of|
|Corps||Command Sergeant Major (CSM)||a few Divisions|
|Division||Command Sergeant Major (CSM)||several Battalions|
|Battalion||Command Sergeant Major (CSM)||two to five Companies|
|Company||First Sergeant (1SG)||several Platoons|
|Platoon||Platoon Sergeant Sergeant First Class||several sections|
|Section||Section Sergeant Staff Sergeant||two or three squads|
|Squad||Squad Leader Sergeant||two or three fire teams|
|Fire team||Fire team Leader Corporal||four to six soldiers|
Naval rates and ranks
The United States Navy uses naval rate for enlisted men and rank for officers. See U.S. Navy enlisted rate insignia and U.S. Navy officer rank insignia for examples. Naval rate should not be confused with naval rating.
- Comparative military ranks for detailed rank listing
- Military unit
- Russian military ranks
- List of US military leaders by rank
For specific insignia and history:
- British Army officer rank insignia
- British Army enlisted rank insignia
- U.S. Army officer rank insignia
- U.S. Army enlisted rank insignia