A division is a large military unit or formation usually consisting of around 10,000 soldiers. In most armies a division is composed of several regiments or brigades, and in turn several divisions make up a corps.
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The term division came into use as armies began to grow and become mass formations. The division was originally an organizational structure under the corps to assist in command and control of various regiments and brigades. The corps remained the primary maneuver unit of the army, while heraldry and unit identification remained primarily a matter of the regiment.
The modern division
In modern times, the divisional structure has been standardized by most military forces. This does not mean that divisions are equal in size or structure from military to military, but generally divisions have in most cases come to be units of 10,000 to 20,000 troops with substantial enough support organic to the unit to be capable of independent operations. Usually the direct organization of the division consists of one to four brigades or regiments of the combat arm of the division along with a brigade or regiment of combat support (usually artillery) and a number of direct-reporting battalions for various specialized support tasks (often reconnaissance and combat engineers). In most militaries, ideal organization strength is standardized for each type of division, encapsulated in a table of organization and equipment, or TO&E, which specifies exact assignments of units, personnel, and equipment for the division.
The modern division has become in many militaries the primary identifiable combat unit, supplanting the regiment. The peak of use of the division as the primary combat unit was during World War II, when hundreds of divisions were deployed. Presently, smaller numbers of divisions represent significant combat power. The recent Invasion of Iraq was completed with only a handful of divisions with significant support forces.
Divisions are often formed to organize units of a particular type together with appropriate support units to allow independent operations. In more recent times, divisions are more often organized as a combined arms unit with subordinate units representing various combat arms. In this case, the division often retains the name of a more specialized division, and may still be tasked with a primary role suited to that specialization.
The most common form of divisions formed throughout most of history have been infantry divisions. Often, in small militaries, all divisions were infantry and therefore the term division is synonymous with infantry division in those forces. The basic infantry division is usually formed with a number of infantry regiments (usually three), an artillery regiment, and a few support battalions.
Infantry divisions are often formed for specific purposes, and these are sometimes reflected in their name. Basic infantry, without its own transportation (thus relying on leg and horse mobility), is in modern times often considered light infantry, thus the formation of the light infantry division. Its primary value in today's military environment is that it is easy to transport and keep supplied due to its lack of heavy equipment. It is ideal for low-intensity conflict, but lacks firepower for full scale warfare.
A common kind of infantry division is mountain infantry. These units are designed to move and fight in alpine environments, and thus their training and equipment must be able to withstand rugged terrain and inclement conditions. Mountain units are often considered elite units, and they may be used in more conventional environments when high-quality troops are needed. Another popular elite infantry formation is the airborne infantry, commonly called parachute infantry. These units are designed to drop their forces by air (both parachute and glider) and maintain combat operations autonomously behind enemy lines. More so than mountain divisions, these units require special training and equipment. A recent off-shoot has been the air-mobile infantry, designed to use helicopter insertion versus traditional airborne operations. All of these units are often employed as elite infantry in traditional combat situations.
During World War II, infantry units began becoming more and more mechanized. Many were given enough trucks to carry their entire force, sometimes becoming known as motorised or motorized infantry. Some were equipped with halftracks and other armored carriers, and were known as armored infantry (Germany's units were given the name Panzergrenadier). As these units were developed after the war, the term motorized became common regardless of the type of transportation. For example, the Soviet Union made wide use of armoured personnel carriers in its motor rifle divisions, as did the United States Army in its infantry (motorized) divisions.
For most nations, cavalry was deployed in smaller units and was not therefore organized into divisions, but for larger militaries, a number of cavalry divisions were formed. They were most often similar to the nations' infantry divisions in structure, although they usually had fewer and lighter support elements, with cavalry brigades or regiments replacing the infantry units. For the most part, large cavalry units did not remain after World War II.
While horse cavalry had been found to be obsolete, the concept of cavalry as a fast force capable of missions traditionally fulfilled by horse cavalry made a return to military thinking during the Cold War. In general, two types of new cavalry were developed: armoured cavalry, based on an autonomous armored formation, and air cavalry, relying on helicopter mobility. The latter was formed into the U.S. 1st Cavalry Division, although this is essentially air-mobile infantry with significant support units.
The development of the tank near the end of World War I prompted some nations to experiment with forming them into division-size units. Many did this the same way as they did cavalry, by merely replacing infantry with tank units and giving motorization to the support units. This proved unwieldy in combat, as the units had many tanks but little infantry. Instead, a more balanced approach of balancing the number of tank, infantry, and artillery units within the division took place.
By the end of World War II, in most cases armoured division referred to divisions with significant tank battalions and motorization for its infantry, artillery, and support units. Infantry division referred to divisions with a majority of infantry units.
Since the end of the war, most armoured and infantry divisions have had significant numbers of both tank and infantry units within them. The difference has usually been in the mix of battalions assigned. Additionally, in some militaries, armored divisions would be equipped with the most advanced or powerful tanks.
In most nations, divisions are designated by combining an ordinal number and a type name. Nicknames are often assigned or adopted although these often are not considered an official part of the unit's nomenclature. In some cases, divisions are titled without an ordinal number, often in the case of unique units, or units serving as elite or special troops. For clarification in histories and reports, the nation is identified previous to the number.
It is important to note that division names are completely subject to the whim of whatever controlling body names the unit. Fanciful and incongruous names are commonly found. It is common for the ordinal number to not be sequential, leading to high numbers without that many divisions existing. Types as well are not always indicative of the actual structure or mission of the unit. Germany raised a parachute armored division (Fallschirmpanzer-Division) during World War II which obviously never conducted, nor was intended to conduct, a parachute drop.
The primary purpose of nomenclature is to give each unit a unique identification to assist in command and control of units. This is also helpful in historical studies, but due to the nature of intelligence on the battlefield, division names and assignments are at times obscured. However, the size of the division makes such obfuscation rarely necessary.
In the United States Army, a divisional unit typically consists of 10,000 to 20,000 troops commanded by a major general. Two divisions usually compose a corps and each division is composed of about 3 brigades, along with a number of smaller specialized units.
The United States Army currently has ten active divisions:
1st Infantry Division at Fort Riley, Kansas and Germany 1st Armored Division at Fort Riley, Kansas and Germany 1st Cavalry Division at Fort Hood, Texas 2nd Infantry Division at South Korea 3rd Infantry Division at Fort Stewart, Georgia 4th Infantry Division at Fort Hood, Texas 10th Mountain Division (Light) at Fort Drum, New York 25th Infantry Division (Light) at Schofield Barracks, Hawaii 82nd Airborne Division at Fort Bragg, North Carolina 101st Airborne Division (Air Assult) at Fort Campbell, Kentucky
In the British Army a division is also commanded by a major-general and consists of three infantry and/or armoured brigades, an artillery brigade, a signal regiment, a logistic regiment, an engineer regiment, and supporting units.