Rethinking International Armed Conflict: Legal Challenges in the Age of Hybrid Warfare

Authors

• Oleksandr Havryshuk
• Roman Hryshchenko

First Page

255

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jurisprudence, and related instruments, and identifies four structural deficiencies: state-centricity, reliance on outdated formalities, indeterminacy of the ""resort to armed force"" standard, and the inability to address PMC operations conducted under effective state control.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 proposes a new formulation — the new definition of IAC — under which an IAC arises whenever one state (or group of states) commits an act of aggression against another state, provided that at least one state involved recognizes itself as the victim of that 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.

Recommended Citation

Oleksandr Havryshuk & Roman Hryshchenko, Rethinking International Armed Conflict: Legal Challenges in the Age of Hybrid Warfare, 51 Brook. J. Int'l L. 255 (2026).
Available at: https://brooklynworks.brooklaw.edu/bjil/vol51/iss2/1