The conduct of warfare is constantly shaped by forces beyond the battlefield. These forces create complexities in the battlespace for military operations. The ever-changing nature of how and where wars are fought creates challenges for the application of the unchanging body of international law that regulates armed conflicts. The term 'complex' is often used to describe modern warfare, but what makes modern warfare complex? Is it the increasingly urbanized battlefield where wars are fought, which is cluttered with civilians and civilian objects? Is it the rise of State-like organized armed groups that leverage the governance vacuum created by failed or failing States? Is it the introduction of new technologies to military operations like autonomous weapons, cyber capabilities, and unmanned aerial systems?