While Unconventional Warfare (UW) remains a viable, low-cost method of indirect warfare, some of the assumptions underpinning traditional UW have diverged from reality in the last two decades. These include the idea that UW occurs mostly within denied areas; the categorisation of resistance movements into underground, auxiliary and guerrilla components; the model of a pyramid of resistance activities becoming larger in scale, more violent and less covert until they emerge ‘above ground’ into overt combat; and the assumption that the external (non-indigenous) component of UW primarily consists of infiltrated Special Forces elements, or support from governments-in-exile. Arguably these assumptions were always theoretical attempts to model a messy reality. But since the start of this century the evolution of resistance warfare within a rapidly changing environment has prompted the UW community to reconsider their relevance. This article examines that evolution and its implications. It begins with a historical overview, examines how drivers of evolutionary change are manifested in modern resistance warfare and considers the implications for future UW.