Just War and Irregular Warfare

“Jus Tumultuarium Bellum, The Right to Irregular War”

Original work By J. David Thompson, U.S. Army Civil Affairs officer

How do we navigate the ethical complexities of irregular warfare in today’s world?

Traditional Just War Theory has guided leaders for centuries, setting standards for when force is justified (jus ad bellum), how it is used during war (jus in bello), and how conflicts are resolved (jus post bellum). But modern conflicts—often involving proxies, non-state actors, and irregular tactics—pose challenges that traditional frameworks fail to address.

This article explores a groundbreaking supplement to Just War Theory: jus tumultuarium bellum, or the “right to irregular war.” It argues for a refined ethical framework that considers the realities of irregular warfare’s “by, with, and through” approach. From ensuring non-state actors’ governance capabilities (“sticking power”) to evaluating proportionality and intent, this framework aims to fill critical gaps in how we ethically assess partnerships in irregular warfare.

Why does this matter?

The U.S. and its competitors—Russia, China, and Iran—extensively leverage irregular warfare, working through proxies like Wagner Group, Hezbollah, and others. Yet, without clear ethical guidelines, states risk exploiting ambiguities that could escalate conflicts or harm civilian populations.

To learn more about how jus tumultuarium bellum reshapes the ethical conversation around irregular warfare, read the full work here.

Photo Credits: Nick Marano, Building Small Unit Leaders in the Long War, Marine Corps Training and Education Command 13