Editing Regiment (section)

== United States ==
{{main|Regiment (United States Army)}}
{{more citations needed section|date=December 2015}}

[[File:US 65th Infantry Regiment.Painting.Korean War.Bayonet charge against Chinese division.jpg|thumb|right|The Puerto Rican [[65th Infantry Regiment (United States)|65th Infantry Regiment]]'s [[bayonet]] charge against a [[People's Volunteer Army|Chinese]] division during the Korean War.]]

Historically, the [[United States Army]] was organized into regiments, except from 1792 to 1796 during the existence of the [[Legion of the United States]]. During this period the Army, or "Legion", was organized into four "sub-legions", 18th century forerunners of the modern [[Brigade Combat Team|combined arms brigade]] that combined infantry, [[rifleman|riflemen]], [[artillery]], and [[cavalry]]. When combined with other regiments during wartime, for active field operations, regiments were further formed into [[brigade]]s and [[Division (military)|divisions]].

From colonial times, the regiment consisted of a small regimental [[Headquarters#Military|headquarters]] (regimental [[Headquarters Company|headquarters companies]] not existing before 1915) and in 1775 ten "line" [[Company (military unit)#United States|companies]], based on the British Army model, without any permanent intermediate level of organization, viz., [[Battalion#United States Armed Forces|battalion]] headquarters organic to the regiment. From 1776 through 1783 American infantry regiments contained from as few as seven companies (e.g. South Carolina Rifles) to as many as twelve (Pennsylvania Rifles and Maryland State troops) with Continental Army infantry regiments having eight companies (increased to nine in 1781). (Briefly, from 1790 to 1792, regiments were organized into three battalions of four companies each.) Traditionally, the regiment and battalion were one and the same, with the "battalion" simply being the regiment organized for battle.

During the Civil War, there were nine new United States regular army infantry regiments (11th though the 19th) added to the ten already existing. The old regiments (1st through 10th) were single-battalion, ten-company regiments, but the new regiments were authorized three battalions of eight companies each.<ref>Mahan, J. and Danysh, R. ''Army Lineage Series, Infantry Part 1: Regular Army.'' (1972) Office of the Chief of Military History, United States Army: Washington, DC. p. 24.</ref> However, only three of these nine regiments ever reached full strength of three battalions, with four others only achieving a manning level of two full battalions.  Regiments were usually commanded by a colonel, assisted by a lieutenant colonel and a major, as well as additional staff officers and enlisted men in the regimental headquarters. Occasionally, a regimental commander would organize several companies into one, or rarely two, temporary organizations, called battalions, under command of the regiment's lieutenant colonel, major, or a senior captain. (A historic example of this arrangement is the 7th Cavalry Regiment during the [[Battle of the Little Big Horn]] in 1876.)

Many more additional regiments of the [[United States Volunteers]] were recruited from each state during the [[American Civil War]] according to General Orders No. 15., War Department, Adjutant General's Office, Washington, May 4, 1861:

{{blockquote|The President of the United States having called for a Volunteer Force to aid in the enforcement of the laws and the suppression of insurrection, and to consist of thirty-nine regiments of infantry and one regiment of cavalry, making a minimum aggregate of (34,506) thirty-four thousand five hundred and six officers and enlisted men, and a maximum aggregate of (42,034) forty two thousand and thirty-four officers and enlisted men, the following plan of organization has been adopted, and is directed to be printed for general information.}}

In 1890, the number of companies in a regiment was reduced from the traditional ten to only eight, as the end of the Indian Wars became evident and troop reductions became in order. However, in 1898 as the war with Spain began, a three-battalion, 12-company structure was effected. This expanded regimental structure produced units, proportionally roughly the same approximate size as the single battalion, ten-company regiments of the Civil War. (For example: 101 officers and enlisted men per company, and a 36-member regimental headquarters, with 1,046 per typical Union Army infantry regiment in 1861, vs. 112 officers and enlisted men per company, and the same 36-member regimental headquarters, with 1,380 per regiment in a typical U.S. Army infantry regiment in 1898.) After the short war the Army reduced the size of companies, battalions, and regiments by about 30% under demobilization. However, the number of companies and battalions per regiment remained at 12 and three, respectively.

Until 1917, under its traditional triangular organizational plan, infantry regiments were organized into brigades of three regiments, with three infantry brigades (for a total of nine infantry regiments), along with one brigade each of cavalry and field artillery constituting a division. In 1917 the Army adopted the [[square division]] organizational plan, which massively increased the size of units from the company through corps, more than tripling, or nearly quadrupling, the number of troops per unit. (From 1915 to 1917, the authorized strength of rifle companies increased from 76 officers and enlisted men to 256, and infantry regiments grew from 959 to 3,720.)

The "square division" consisted of two infantry brigades of two infantry regiments each, with each regiment containing a regimental headquarters company, a machinegun company, a supply company, and 12 rifle companies organized into three battalions of four rifle companies each. (The single machine gun company reported directly to regimental headquarters.) The division also contained an artillery brigade of three regiments and three separate combat service support regiments: engineer, quartermaster, and medical.

The Army reorganized in preparation for the Second World War by effecting its [[triangular division]] organizational structure in 1939. Under this plan, divisional brigades were eliminated and the division consisted of three infantry regiments and one artillery regiment, styled as "Division Artillery", but usually consisting of battalions of the same regiment. The infantry regiments still contained three battalions; there were now "headquarters and headquarters" companies (HHCs) not only at the regimental-level but in each battalion as well. The battalions still contained four "line" companies, but instead of four rifle companies, now had three rifle companies and a heavy weapons company (containing machine guns and mortars). The regiment's machine gun company became an anti-tank company, the supply company became the service company, and a cannon company and a medical detachment were added to the regiment. In 1942 the Army began organizing armored divisions into [[combat command]]s, which grouped armor, armored infantry, and armored field artillery battalions into three tactical groups within the division without regard to regimental affiliation. However, armored regiment designations were retained for lineage and heraldic purposes.

As the United States Army transformed after the Korean War for potential combat against a nuclear-armed Warsaw Pact, changes began in 1956 to transform infantry regiments into [[Battlegroup (army)|battle groups]] under its new [[Pentomic]] organization.{{sfn|Bacevich|1986}} Under this plan, battalions were eliminated and the infantry battle groups consisted of an [[Headquarters and Headquarters Company]], five rifle companies, and a combat support company. This scheme retained the regimental designation for lineage and heraldry purposes, but the regiment ceased to exist as an intact organization for both infantry and field artillery units. The Divisional Artillery were now composed of several unrelated artillery battalions.

By 1965, the Army had eliminated the regiment (replaced by the brigade) under the [[Reorganization Objective Army Divisions]] (ROAD) plan as a tactical and administrative organization in all combat arms, save for a few armored cavalry regiments. However the battalion was restored as a tactical echelon, now organized into an HHC, three rifle companies, and a combat support company. The ROAD structure sealed the fate of the regiment in the U.S. Army, confirming its elimination as a level of command that had begun in 1942 with the "combat command" organization of the armored divisions and furthered by the Pentomic experiment in the 1950s. By 2015, the only Army unit still organized as a traditional regiment was the [[75th Ranger Regiment]].

In the 20th century, by using modern industrial management techniques, the Army was able to draft, assemble, equip, train and then employ huge masses of conscripted civilians in very short order, starting with minimal resources. Beginning with the First World War, as units became increasingly larger, and weapon systems and equipment became more complex, the regiment, while still filling a role as the immediate headquarters for its organic battalions, began to be replaced by the brigade as the intermediate tactical and operational headquarters for battalions, with the division becoming the senior administrative and logistical headquarters for the battalions, regiments, and brigades under its command.

A new system, the [[Combat Arms Regimental System]], or CARS, was adopted in 1957 to replace the old regimental system. CARS uses the Army's traditional regiments as parent organizations for historical purposes, but the primary building blocks are [[Division (military)|divisions]], [[brigade]]s, and [[battalion]]s. Each battalion carries an association with a [[parent regiment]], even though the regimental organization no longer exists. In some brigades several numbered battalions carrying the same regimental association may still serve together, and tend to consider themselves part of the traditional regiment when in fact they are independent battalions serving a brigade, rather than a regimental, headquarters.

The [[United States Army Regimental System]] (USARS) was established in 1981 to replace the Combat Arms Regimental System, to provide each soldier with continuous identification with a single regiment, and to support that concept with a personnel system that would increase a soldier's probability of serving recurring assignments with his or her regiment. The USARS was developed with the intention that it would enhance combat effectiveness by providing the opportunity for a regimental affiliation, thus obtaining some of the benefits of the traditional regimental system.

Exceptions exist to USARS regimental titles, including the [[armored cavalry regiment]]s (now defunct) and the [[75th Ranger Regiment]] created in 1986. On 1 October 2005, the word "regiment" was formally appended to the name of all active and inactive CARS and USARS regiments. So, for example, the 1st Cavalry officially became titled the 1st Cavalry Regiment.

=== United States Marine Corps ===
{{Main list|List of United States Marine Corps regiments}}
{{more citations needed section|date=December 2018}}
The historical background of the use of regiments in the United States Marine Corps (USMC) is contained within ''USMC: A Complete History''<ref>Hoffman, J. ''USMC: A Complete History.'' (2002) Marine Corps Association: Quantico, VA.</ref> and a summary of that information follows:

From the American Revolution until 1913 it was common practice for USMC detachments (both ship-based, and shore-based) to be combined to form provisional units. Most often these formations took the form of provisional [[battalion]]s, but on occasion became provisional regiments, provisional [[brigade]]s, or rarely (especially when combined with Navy personnel) [[naval infantry]] brigades.<ref name="NavalHistoryandHeritageCommand">{{Cite web |title=Sailors as Infantry in the US Navy |url=https://www.history.navy.mil/content/history/nhhc/research/library/online-reading-room/title-list-alphabetically/s/sailors-as-infantry-us-navy.html |access-date=2022-08-14 |website=NHHC |language=en-US}}</ref> These organizations were intentionally temporary as the USMC did not usually maintain standing forces larger than company size, but rather created "task units" on an "as needed" basis.

While provisional regiments, designated variously as the 1st through 4th Regiments, had been formed for expeditionary operations in Panama (1895) and Philippines (1899),<ref name=NavalHistoryandHeritageCommand/> the lineage of modern USMC regiments began in 1913 with the creation of the 1st and 2nd [[Advanced Base Force]] Regiments. These two regiments, (currently the [[2nd Marines|2nd]] and [[1st Marines]], respectively), along with the numerical forebears of the [[3rd Marines|3rd]] and [[4th Marines]], (formed in 1914 for the short-lived [[Tampico Affair]] with Mexico, involving the [[occupation of Veracruz]]), are the pre-World War I antecedents to the several regiments of the modern USMC.

Beginning in World War I, with the USMC's participation with the U.S. Army in the [[American Expeditionary Force]], in which the [[5th Marines|5th]] and [[6th Marines]] (along with the [[6th Machine Gun Battalion (United States Marine Corps)|6th Machine Gun Battalion]]) formed the [[4th Marine Expeditionary Brigade#History|4th Marine Brigade]] of the U.S. Army [[2nd Infantry Division (United States)|2nd Division]], the USMC began organizing larger standing forces. World War I–era USMC units mirrored equivalent U.S. Army units by employing the "square division" organizational plan in forming its regiments and brigades.

During the Second World War, the USMC organized its regiments and divisions under the "triangular division" model developed by the Army in 1939. Modern USMC regiments and divisions continue to be organized using a triangular model very similar to the WWII version, with slight variations to adapt to modern weapons, equipment, and enlisted rank structure.

Current Marine infantry, field artillery, and combat logistics battalions are organized into regiments, commanded by a colonel. Marine infantry and field artillery regiments are sequentially numbered and are referred to generically as "''n''th Marines" or "''n''th Marine Regiment", as in 1st Marines (an infantry regiment) or 12th Marine Regiment (a field artillery regiment). Marine infantry regiments consist of a regimental headquarters and service company (H&S Co) and three identical infantry battalions. Marine field artillery regiments consist of a regimental headquarters and service battery (H&S Bttry), a target acquisition battery, and from two to four field artillery battalions.

[[Marine logistics group]]s (MLG) contain two types of regiments; one headquarters (HQ) regiment (except in the Reserve 4th MLG) and two combat logistics regiments (CLR). Each of these two types of regiments contain a headquarters company and varying numbers and types of logistics battalions and separate logistics companies, depending upon whether the regiment's primary mission is to provide direct support to (1) a [[regimental combat team]] (RCT) or a [[Marine amphibious unit]] (MEU), or (2) provide general support across the [[Marine expeditionary force]] (MEF), including intermediate ground logistics support to Marine aviation units. These varying types of battalions and separate companies include: combat logistics, maintenance, and supply battalions, and combat logistics, communications, food service, and service companies (the latter three types in 3rd MLG only).

The HQ regiments (whose primary mission includes providing support to the MEUs) are not numbered; however, the CLRs are numbered according to their primary mission. CLRs that support RCTs have the same number as the parent Marine division of its supported RCT. Therefore, CLR 2 supports the RCTs of the 2nd Marine Division. CLRs that provide general maintenance and supply support to the MEF are designated by a two-digit number: the first digit is the Hindu-Arabic numeral equivalent of the MEF's roman numeral designation, and the second digit is always an arbitrarily assigned numeral "5". Therefore, the CLR that provides general maintenance and supply support to III MEF is CLR 35.

The USMC deploys [[battalion]]s from its infantry regiments to form the nucleus of a [[battalion landing team]] (BLT) as the [[ground combat element]] (GCE) of a [[Marine expeditionary unit]] (MEU). However, a USMC infantry regiment may deploy en masse to form the nucleus of an RCT or regimental landing team (RLT) as the GCE of a [[Marine expeditionary brigade]] (MEB). In both cases the infantry component is reinforced with ground combat support forces including field artillery, reconnaissance, assault amphibian vehicle, light armored reconnaissance vehicle, tank, and combat engineer units. The resulting GCE is then combined with an [[aviation combat element]] (ACE), a [[logistics combat element]] (LCE), and a [[command element (United States Marine Corps)|command element]] (CE) to form a [[Marine air-ground task force]] (MAGTF).