Cyberspace and its associated operations present both opportunities and challenges for military and United States Government decision-makers and planners. The Pentagon has formally recognized cyberspace as a domain of warfare. Cyberspace is man-made, dynamic, and intrinsically linked to not only Department of Defense (DoD) capabilities across the other four domains, but also to national, commercial and global capabilities and interests as well. The implications for cyberspace, its defense and freedom of operations within, extend well beyond DoD's, and even the U.S. Government's, span of control and influence. Increasingly, foreign influence and threats are shaping the cyber battlefield. In order to effectively navigate the complexities posed by cyberspace and ensure that the United States gains and maintains strategic advantage in the future battlefield using cyberspace operations, a whole-of-government approach is required. The United States will need to leverage the unique capabilities of the various actors across the diplomatic, information, military, economic, financial, intelligence, and law enforcement (DIMEFIL) spectrum to successfully defend against the asymmetric threats posed in cyberspace while ensuring freedom of action within the domain. This book examines the current strategic guidance, organizational framework, governance and responsibilities associated with cyberspace operations. It identifies the issues and challenges currently facing the U.S. in operationalizing a whole-of-government approach to defending and operating in the cyberspace domain. Finally, this book presents recommendations for improvements in the implementation and operationalization of a whole-of-government approach to cyberspace operations.