Just War and Irregular Warfare
Jus Tumultuarium Bellum, The Right to Irregular War
By J. David Thompson, U.S. Army Civil Affairs officer
Photo provided by Adobe Stock
Just War Tradition, also called Just War Theory, provides the ethical framework that governs when a state can
resort to force (jus ad bellum), conduct during conflict (jus in bello), and ending conflict (jus post bellum).
It has been used by philosophers, military practitioners, and heads of state since the times of Cicero and Saint
Augustine. 01
The resort to force ethics details who could declare a war. It provides what equals a just cause for war, ensures
the war aims were proportional to the harm inflicted, requires exhausting peaceful alternatives, mandates that
parties have the right intent, and necessitates that there is a reasonable chance of success. The conduct during
conflict criteria are equally clear: forcing combatants to distinguish civilians from belligerents and ensuring
the means of response are not excessive. The ending conflict criteria, while relatively lesser developed, detail
the rights and responsibilities between parties to a conflict post hostilities. This model worked out well
during the “good ol’ days” of war—war was declared, one side won, the other side lost,
and everyone went home. 02
In the modern era, war emerges along a continuum of competition ranging from competition below armed conflict,
crisis, and armed conflict. 03 The
range of military options available to defense and policy leaders consist of less than lethal options inherent
in irregular warfare activities. Irregular warfare provides opportunities of conducting operations through
proxies. These opportunities contrast with more lethal traditional warfare alternative in large scale combat
operations (LSCO). Despite the familiarity with irregular and conventional warfare alternatives, Just War
Tradition fails to provide an adequate ethical framework for leveraging irregular warfare options. This creates
an opportunity for a new ethical framework to augment Just War Tradition—jus tumultuarium bellum (right to
irregular war). Ethics matter, even though ethical judgments lack the finality of a legal judgment, because
ethics tell us what should be. The 2022 National Defense Strategy anchors defense strategy in partners and
allies. 04 Thus, it is important
to consider the ethics of our partners and allies. This paper seeks to fill the gap by providing an ethical
framework on forming proxy relations in irregular warfare.
In irregular warfare, the United States works “by, with, and through regular forces, irregular forces, and
individuals,” 05 through
“indirect, non-attributable, or asymmetric activities.” 06 The U.S. leverages irregular warfare activities
in support of theater campaigns against competitors like China, Russia, Iran, and others. These competitors also
work “by, with, and through” their own proxies. For example, China seeks military objectives through
Chinese businesses. 07 Meanwhile,
Russia notoriously works through Wagner and other private military and security companies. 08 And then there is Iran, who sponsors Hezbollah
in Lebanon, Hamas in Gaza, the Houthis in Yemen, and other non-state armed groups in Iraq, Syria, and elsewhere.
09 Despite these fairly obvious
opportunities, there remains no ethical framework upon which our practitioners and theorists can model the
analysis and potential employment of “by, with, and through” partners in irregular warfare.
To the benefit of our government and defense officials, this paper presents a narrow focus to renegotiate part of
right to war ethics with irregular warfare’s “by, with, and through.” Jus ad bellum, the right
to wage war, fails to delineate the ethical criteria necessary to form partnerships and supportive arrangements
in war. States have found tactical and political advantages to this ethical ambiguity. States can shift some of
the risks in waging war to an indigenous, non-state force. 10 There is a gap surrounding irregular warfare’s “by, with,
and through” indigenous, non-state actors about what rules apply, and who do they apply to? The resort to
force by a state is stepping over a bright line, both legally and ethically. Supporting an irregular force or
non-state actor in a pre-existing conflict presents several challenges. First, it is unclear what degree of
support makes a state a party to a conflict. 11 Second, it is unclear whether the state creates an international armed
conflict against a state or whether the state becomes party to a pre-existing non-international armed conflict
between the state and the non-state. 12 These ambiguities provide legal and ethical loopholes for states to
pursue desired policy outcomes with limited tactical and political exposure.
“Just War Tradition, also called Just War Theory, provides the ethical framework that governs when
a state can resort to force (jus ad bellum), conduct during conflict (jus in bello), and ending conflict (jus
post bellum).”
To fill this ethical gap, the proposed framework is called jus tumultuarium bellum, and it seeks to augment
contemporary Just War Tradition. In the jus tumultuarium bellum party, states and non-states have to fulfill the
traditional resort to force criteria. The criteria includes: just authority, just cause, proportionality,
exhausting peaceful alternatives, right intention, and chance of success. In addition to solely fulfilling the
resort to force criteria, parties must make an ethical determination about the justness of the other’s
resort to force responsibilities. If the other actors fail to meet the criteria then the parties should not
partner.
In addition to determining the justness of the other’s resort to force responsibilities, jus tumultuarium
bellum borrows from the emergent jus ad vim (just use of force) thinking that irregular warfare should not
escalate the conflict. 13 If part
of the intent of the irregular warfare campaign is to conduct a conflict short of LSCO then irregular warfare
should not increase the probability of resorting to LSCO.
Jus tumultuarium bellum also requires that the state ensures the non-state actor has “sticking
power.” Deciding to wage war requires mobilizing troops, acquiring arms, raising money to fund the
conflict and, ultimately, issuing orders to kill. 14 To carry the ethical burden, it is necessary that the non-state actor be
able to prevail after the conflict. This requires that the non-state actor be representative of the population
it is fighting for and have capabilities to provide governance. 15 This is a higher standard than that of states. States do not have to be
a representative, and they barely have to be capable. Yet states are generally presumed just authorities in the
international community. Despite this difference, if a state is to support a non-state in an armed conflict then
the non-state should be able to survive after the conflict. 16
Lastly, jus tumultuarium bellum recognizes that traditional notions of resort to force ethics may fall short. For
example, under traditional Just War Tradition, a resort to conflict is justified only in response to unlawful
aggression, pre-emption of an imminent attack, in pursuit of self-determination against a colonial or racist
regime, or in support of humanitarian intervention. States, for example, are unlikely to wait for unlawful
aggression to initiate irregular warfare. Large-scale combat operations are more apt to respond to unlawful
aggression than focusing on “by, with, and through.” Irregular warfare can also be a step in
exhausting peaceful alternatives. For a state partnering with a non-state, the proportionality of harm caused by
the state is less than LSCO. Continued waiting may help fulfill traditional notions of exhausting peaceful
alternatives; however, it will likely increase the totality of harm should a state later face unlawful
aggression. Therefore, irregular warfare’s “by, with, and through” challenges just cause,
necessity, proportionality, and chance of success. Thus, irregular warfare challenges traditional notions of
resort to force ethics. Therefore, it is necessary that states and non-states analyze traditional notions of
resort to force ethics with jus tumultuarium bellum.
The proposed ethical framework will not be without its doubters. Just War thinking has three main camps:
Orthodox, Revisionists, and Neoclassical. Orthodox scholars follow the legalist position popularized by Michael
Walzer, an American professor emeritus and political theorist. Revisionists seek to revisit the Orthodox’s
moral equivalency of combatants but have yet to develop a comprehensive framework. Neoclassical scholars turn
more to the writings of Saint Augustine, Thomas Aquinas, Hugo Grotius, and others. Revisionist Just War scholars
are unlikely to support the proposed jus tumultuarium bellum. Per most Revisionists, there is only a need for
one framework: that of international human rights law. Revisionists, amongst other things, question the need for
a separate ethical framework that solely governs armed conflict. 17 The Orthodox and Neoclassical interpretations of
Just War Tradition are more apt to see the benefit that jus tumultuarium bellum can provide. Ultimately, however
analyzed, Just War Tradition fails to provide an adequate vocabulary and framework to discuss irregular
warfare’s “by, with, and through” without jus tumultuarium bellum. The proposed framework
gives philosophers, practitioners, and the public a way to explain and think about one of the realities of war.
This paper identified a shortcoming in the philosophy that seeks to govern the resort to war, conduct in war, and
responsibilities when ending war. It sought to fill this gap by proposing a supplemental moral philosophy called
jus tumultuarium bellum. Jus tumultuarium bellum requires both parties to fulfill individual right to war
criteria. It also asks each party to make a determination of the other’s justness in fulfilling its right
to war responsibilities. It requires a “sticking power” for the non-state actor. Lastly, jus
tumultuarium bellum recognizes that traditional notions of the right to war may fall short in irregular warfare.
Therefore, it is necessary that states and non-states analyze traditional notions of resort to force ethics with
jus tumultuarium bellum before deciding to enter a supportive relationship in irregular warfare’s
“by, with, and through.”
Notes
01. Bellamy, A., (10 November 2006), “Just Wars:
From Cicero to Iraq.”
02. Whetham, D. G. (2016). “Are We Fighting
Yet?” Can Traditional Just War Concepts Cope with Contemporary Conflict and the Changing Character
of War, MONIST, 99(1), 55-69. https://doi.org/10.1093/monist/onv029.
03. Department of the Army, (2022), “FM 3-0,
Operations,” 1-14.
06. Department of Defense, (2019), Doctrine of the
Armed Forces of the United States. Vol. 1. Washington D.C., USA. There are multiple competing, and at
times conflicting, definitions of irregular warfare. The 2024 National Defense Authorization Act (NDAA)
defines irregular warfare 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.” DoD defines irregular warfare in JP 1,
Vol 1: ‘[a] form of warfare where states and non-state actors’ campaign to assure or coerce
states or other groups through indirect, non-attributable, or asymmetric activities.” Army defines
irregular warfare in FM 3-0, “[t]he overt, clandestine, and covert employment of military and
non-military capabilities across multiple domains by state and non-state actors through methods other
than military domination of an adversary, either as the primary approach or in concert with conventional
warfare.”
07. Department of Defense, (2023), 2023 Report on the
Military and Security Developments Involving the People’s Republic of China, 30.
11. Cuyckens, H., “How to stay neutral in 2022?
A practical approach,” Proceedings of the Bruges Colloquium, 71-75. See also Bothe, M., “The
Law of Neutrality in the XXIst century: evolution or revolution?” Proceedings of the Bruges
Colloquium, 66-70.
12. de Saint Maurice, T., “Classifying conflicts
in 2022 – reflections on a practical challenge,” Proceedings of the Bruges Colloquium,
22-26.
13. Brunstetter, D. and Braun, M., (14 February 2013),
“From Jus ad Bellum to Jus ad Vim: Recalibrating Our Understanding of the Moral Use of
Force,” Ethics in International Affairs,
14. Gross, M., (12 January 2015) “The Ethics of
Insurgency: A Critical Guide to Just Guerrilla Warfare,” 37.
15. Gross, M., (12 January 2015) “The Ethics of
Insurgency: A Critical Guide to Just Guerrilla Warfare,” Ch 1.
16. For more on this, see: Gross, M., (12 January
2015) “The Ethics of Insurgency: A Critical Guide to Just Guerrilla Warfare.” See also
Staniland, P., (2014), “Networks of Rebellion: Explaining Insurgent Cohesion and Collapse.”
17. Braun, C., (2023), “Limited Force and the
Fight for the Just War Tradition,” 5.
Note: J. David Thompson is a U.S. Army Civil Affairs officer with multiple deployments to
Afghanistan, Jordan, and Iraq. He holds a Juris Doctorate from Washington and Lee University School of Law.
He is a PhD Candidate at King’s College London.