In a 2002 article, Michael N. Schmitt predicted that twenty-first century warfare would differ dramatically from warfare in the twentieth century. Writing at a time when transnational terrorism was dominating the headlines, Schmitt nonetheless claimed that it was information warfare that would ‘challenge existing doctrine on the waging of war, necessitate a revised concept of battle space and expand the available methods and means of warfare’ (2002: 365). A decade on, few would disagree with Schmitt’s analysis. The prospect of cyber warfare is necessitating a revised understanding of battle spaces. But what Schmitt could not have foreseen was that transnational terrorism, rather than cyber warfare, would first drive a rethinking of the battle space and the reconceptualisation of the spatial reach of the law of armed conflict. For the next decade, nearly every aspect of international law involving the use of force and the law of armed conflict was contested, dissected, reconstituted. Was transnational terrorism subject to the law of armed conflict or better governed by the law enforcement paradigm? Were terror suspects ‘unlawful enemy combatants’ or criminals? If the law of armed conflict applied, was the ‘war on terror’ an international or non-international armed conflict? As experts disagreed on these and other legal questions, there were increasing calls for new law to govern a new type of war (see Schondorf 2004; Corn and Talbot 2009). And at the root of all these questions was the geography question: where precisely is the battle space?