The world has become more complex, with seemingly unpredictable irregular conflicts taking place around the globe. But there is a pattern to these clashes. They are not unpredictable but discernable. The sources of instability in the 21^st Century's conflict environment will largely result from the interplay between a proliferation in the number of weak and failing states with powerful armed groups, some of which are capable of causing major geopolitical damage in their own territory and beyond. Since the end of the Cold War, an array of armed groups has burgeoned in number and in the capabilities they have to conduct activities. They are diverse in terms of subtypes – terrorists, insurgents, criminals, militias – each varying in vision, mission, and capabilities employed. Local, regional, and global armed groups can now challenge even major states in ways, and to degrees, not possible in the past. This essay presents an analytic delineation and assessment of the makeup of 21^st Century armed groups and the sources of their empowerment.