International relations theory, analysis, policy, and strategy were derived from experiences in the nineteenth and twentieth centuries and, therefore, were built on the assumptions that states are the relevant entities in world politics, and agreements among states will reduce the potential for conflict and violence. This traditional view respects national borders and territorial integrity and assumes that cross-border transgressions are exceptions. But some critical features of cyberspace do not correspond with this traditional view of the state system and the usual ways that nations engage in politics and conflict. Cyberspace has created new ways to aggravate global tensions and new opportunities for avoiding conflict. Already, new patterns of cyber-based conflict have been exposed, from transnational crime and espionage to cyberwar that could disrupt military systems, shut down government servers, or damage critical infrastructure. While there is some emergent cooperation in regard to cyberspace, such as cyber-crime treaties, these efforts are just beginning. An understanding of how the cyber domain influences international relations theory and practice—including its implications for power, politics, conflict, and war—is crucial to the expansion and success of such efforts.