Rethinking International Armed Conflict: Legal Challenges in the Age of Hybrid Warfare
Oleksandr Havryshuk & Roman Hryshchenko
Brooklyn Journal of International Law, vol. 51, no. 2, p. 255 (2026) · Peer-reviewed
Posted July 27, 2026
About this publication
In 2025 the ICRC counted more than 120 active hostilities across over sixty countries, involving upwards of 130 non-state armed groups. The test for identifying an international armed conflict dates to the 1949 Geneva Conventions, and states that start wars have learned to work around it — because the identification decides which protections apply, and whether there is anything to prosecute.
West Support took the decision to address this directly. Our team of researchers has published a peer-reviewed article in the Brooklyn Journal of International Law.
The subject is the identification of the existence of an international armed conflict. The article examines the definitions currently in force, sets out where they fail against the realities of modern warfare, and weighs the consequences of getting the identification wrong.
On the evidence of two conflicts — Ukraine (2014–2022) and Afghanistan (2001–2021) — the article shows that the existing definitions classified them wrongly, and sets out a new one: an international armed conflict exists where an act of aggression has been perpetrated by one state against another, provided that at least one state involved recognises itself as the victim of that aggression. The authors name it the Havryshuk Definition of IAC, and formulate it to prevent such errors.
The authors' abstract follows in full.
Abstract
The binary classification of armed conflicts under international humanitarian law (IHL) — distinguishing international armed conflicts (IACs) from non-international armed conflicts (NIACs) — was forged in the aftermath of World War II and increasingly fails to capture the realities of twenty-first century warfare. Hybrid tactics, cyber operations, the proliferation of private military companies (PMCs), the expanding role of non-state actors, and the near-disappearance of formal declarations of war have eroded the analytical utility of the existing framework, generating legal uncertainty and weakening protections for affected populations. This Article critically examines the conceptual foundations of IAC as set out in Common Article 2 of the Geneva Conventions, the Tadić jurisprudence, and related instruments, and identifies four structural deficiencies: state-centricity, reliance on outdated formalities, indeterminacy of the "resort to armed force" standard, and the inability to address PMC operations conducted under effective state control. Drawing on doctrinal and comparative legal analysis, quantitative conflict data, and interdisciplinary perspectives, the Article introduces the "Havryshuk Definition of IAC" — a new legal formulation stating that an international armed conflict is defined as a situation in which an act of aggression has been perpetrated by one state (or group state) against another state, on the condition that at least one state involved recognizes itself as the victim of said aggression. Through detailed case studies of Afghanistan (2001–2021) and Ukraine (2014–2022), the Article demonstrates how the proposed definition both clarifies ambiguous classifications and forecloses the strategic mischaracterization of conflicts by aggressor states employing hybrid warfare. The Article concludes with concrete proposals for integrating the revised definition into existing IHL frameworks, developing criteria for identifying acts of aggression, establishing mechanisms for state recognition of victimhood, and adapting the definition to hybrid and asymmetric forms of conflict.
Abstract as published by the authors.
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How to cite
Oleksandr Havryshuk & Roman Hryshchenko, Rethinking International Armed Conflict: Legal Challenges in the Age of Hybrid Warfare, 51 Brook. J. Int'l L. 255 (2026).
Cite the published version above. The preprints below are earlier drafts, deposited before publication, and carry their own separate identifiers.
Preprints & indexes
- SSRNdoi.org/10.2139/ssrn.7088679
- ResearchGatedoi.org/10.13140/RG.2.2.28018.88001
- OpenAlexW7167879545