# Irregular warfare

Irregular warfare (IW) is defined in United States joint doctrine as "a violent struggle among state and non-state actors for legitimacy and influence over the relevant populations" and in U.S. law as "Department of Defense activities not involving armed conflict that support predetermined United States policy and military objectives conducted by, with, and through regular forces, irregular forces, groups, and individuals." In practice, control of institutions and infrastructure is also important. Concepts associated with irregular warfare are older than the term itself.
Irregular warfare favors indirect warfare and asymmetric warfare approaches, though it may employ the full range of military and other capabilities in order to erode the adversary's power, influence, and will. It is inherently a protracted struggle that will test the resolve of a state and its strategic partners.
The term "irregular warfare" in Joint doctrine was settled upon in distinction from "traditional warfare" and "unconventional warfare", and to differentiate it as such; it is unrelated to the distinction between "regular" and "irregular forces".

## Terminology
### Early usage

One of the earliest known uses of the term irregular warfare is Charles Edward Callwell's classic 1896 publication for the United Kingdom War Office, Small Wars: Their Principles and Practices, where he noted in defining 'small wars':
"Small wars include the partisan warfare which usually arises when trained soldiers are employed in the quelling of sedition and of insurrections in civilised countries; they include campaigns of conquest when a Great Power adds the territory of barbarous races to its possessions; and they include punitive expeditions against tribes bordering upon distant colonies....Whenever a regular army finds itself engaged upon hostilities against irregular forces, or forces which in their armament, their organization, and their discipline are palpably inferior to it, the conditions of the campaign become distinct from the conditions of modern regular warfare, and it is with hostilities of this nature that this volume proposes to deal. Upon the organization of armies for irregular warfare valuable information is to be found in many instructive military works, official and non-official."
A similar usage appears in the 1986 English edition of "Modern Irregular Warfare in Defense Policy and as a Military Phenomenon" by former Nazi officer Friedrich August Freiherr von der Heydte. The original 1972 German edition of the book is titled "Der Moderne Kleinkrieg als Wehrpolitisches und Militarisches Phänomen". The German word "Kleinkrieg" is literally translated as "Small War." The word "Irregular," used in the title of the English translation of the book, seems to be a reference to non "regular armed forces" as per the Third Geneva Convention.
Another early use of the term is in a 1996 Central Intelligence Agency (CIA) document by Jeffrey B. White. Major military doctrine developments related to IW were done between 2004 and 2007 as a result of the September 11 attacks on the United States. A key proponent of IW within US Department of Defense (DoD) is Michael G. Vickers, a former paramilitary officer in the CIA. The CIA's Special Activities Center (SAC) is the premiere American paramilitary clandestine unit for creating and for combating irregular warfare units. For example, SAC paramilitary officers created and led successful irregular units from the Hmong tribe during the war in Laos in the 1960s, from the Northern Alliance against the Taliban during the war in Afghanistan in 2001, and from the Kurdish Peshmerga against Ansar al-Islam and the forces of Saddam Hussein during the war in Iraq in 2003.

### Other definitions

* IW is a form of warfare that has as its objective the credibility and/or legitimacy of the relevant political authority with the goal of undermining or supporting that authority. IW favors indirect approaches, though it may employ the full range of military and other capabilities to seek asymmetric approaches in order to erode an adversary's power, influence, and will.
* IW is defined as a violent struggle among state and non-state actors for legitimacy and influence over the relevant population(s)
* IW involves conflicts in which enemy combatants are not regular military forces of nation-states.
* IW is "war among the people" as opposed to "industrial war" (i.e., regular war).

## Examples

Nearly all modern wars include at least some element of irregular warfare. Since the time of Napoleon, approximately 80% of conflict has been irregular in nature. However, the following conflicts may be considered to have exemplified by irregular warfare:
* Afghan Civil War
* Algerian War
* American Indian Wars
* American Revolutionary War
* Arab Revolt
* Chinese Civil War
* Cuban Revolution
* First Chechen War
* First Sudanese Civil War
* Iraq War
* Kosovo War
* Lebanese Civil War
* Portuguese Colonial War
* Rwanda Civil War
* Second Boer War
* Second Chechen War
* Second Sudanese Civil War
* Somali Civil War
* Philippine-American War
* The Troubles
* Vietnam War
* Libyan Civil War (2011)
* Syrian Civil War
* Iraqi Civil War (2014–2017)
* Second Libyan Civil War
* Yemeni Civil War (2015–present)

## Activities

Activities and types of conflict included in IW are:
* Asymmetric warfare
* Civil-military operations (CMO)
* Colonial war
* Foreign internal defense (FID)
* Guerrilla warfare (GW)
* Insurgency/Counter-insurgency (COIN)
* Law enforcement activities focused on countering irregular adversaries
* Military Intelligence and counter-intelligence activities
* Stabilization, Security, Transition, and Reconstruction Operations (SSTRO)
* Terrorism/Counter-terrorism
* Transnational criminal activities that support or sustain IW:
** narco-trafficking
** Illicit arms trafficking
** illegal financial transactions
* Unconventional warfare (UW)
According to the DoD, there are five core activities of IW:
* Counter-insurgency (COIN)
* Counter-terrorism (CT)
* Unconventional warfare (UW)
* Foreign internal defense (FID)
* Stabilization Operations (SO)

## Modeling and simulation

As a result of DoD Directive 3000.07, United States armed forces are studying irregular warfare concepts using modeling and simulation.

## Wargames and exercises

There have been several military wargames and military exercises associated with IW, including:
* Unified Action,
* Unified Quest,
* January 2010 Tri-Service Maritime Workshop,
* Joint Irregular Warrior Series war games,
* Expeditionary Warrior war game series, and
* a December 2011 Naval War College Maritime Stability Operations Game focused specifically on stability operations in the maritime domain conducted by the Naval Service.