Editing Regiment (section)

=== 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).