This thesis examines the application of Artificial Intelligence (AI) in the security field, with a particular focus on the European Union as a regulatory and strategic actor within the broader international security environment. It argues that AI constitutes not merely a technological innovation but a structural force reshaping military operations, internal security practices, and the governance of risk across Europe. Drawing on realism, liberalism, and constructivism, the study situates AI at the intersection of geopolitical competition, institutional governance, and normative contestation, highlighting the distinctive role of the EU in promoting human-centric and rights-based approaches to AI governance. The analysis explores key AI-enabled security applications in military affairs, cybersecurity, and hybrid threats, with particular attention to autonomous systems, data driven surveillance, and algorithmic decision-support tools. A case study of the Russia Ukraine war is employed to illustrate the operational relevance of AI-enabled capabilities, including drones, intelligence systems, cyber operations, and influence activities, while also exposing vulnerabilities, escalation risks, and strategic dependencies relevant to European security. The thesis further examines the legal implications of AI through the lenses of international humanitarian law, human rights law, and European Union law. Particular emphasis is placed on the EU Artificial Intelligence Act and its interaction with existing regulatory frameworks such as the General Data Protection Regulation, highlighting challenges related to accountability, proportionality, and civil–military governance asymmetries. Ethical considerations, including the responsibility gap, meaningful human control, and the diffusion of digitally authoritarian practices, are assessed in light of the EU’s normative commitments. The thesis concludes that the effectiveness of the EU’s approach depends on its ability to align regulatory leadership with security capabilities, strengthen institutional oversight, and sustain credible international norms while preserving democratic values.