Introduction

While it is almost trite to emphasize that non-international armed conflict (NIAC) is the predominant form of armed conflict today, less well-known is that ‘irregular’ or ‘guerrilla’ warfare has been the predominant form of warfare throughout human history. The ancient city-states of Mesopotamia, the Han dynasty of imperial China, and the Roman and British Empires were all confronted by various forms of civil strife or insurgent citizenry that challenged their authority through armed resistance. Moreover, these ancient and asymmetric rebellions reveal that many of the defining features of modern NIACs, including foreign fighters, targeted killings, and acts of terror, are far from novel, but rather, have been defining features of ‘irregular warfare’ for thousands of years. What is a comparatively recent development, however, are the various ad hoc efforts to define, classify, and regulate rebellions and insurgencies within international law.