What is the Utility of the Fifth Domain?

The increasing importance of cyberspace for military operations has led to the United States Department of Defense classifying it as the Fifth Domain of Warfare. However, cyberspace lacks the explicit physical properties of land, sea, air and space, and as a consequence its classification as a warfighting domain is controversial. The cyber debate is replete with hyperbole and ambiguous terminology and there are calls to limit the militarization of cyberspace. The critical dependence of Western military forces on microprocessor technology inevitably means that exploiting this domain is viewed from the dual perspectives of opportunity and vulnerability. But does it make any sense to classify cyberspace as a domain? This paper assesses the utility of the Fifth Domain with the aim of understanding what ‘domain status’ means for military forces, how existing theories of war apply to the new domain, and the practical implications of integrating cyberspace operations into warfare.