This handbook assesses and discusses the topic of international security, paying attention both to great powers, and smaller actors. In addition to traditional security topics, it also covers topics on international law, international organisations, globalisation, and transnational challenges.

Consisting of 62 chapters, the handbook is divided into four parts: (1) Complexity of International Security; (2) Material Geographies and Contemporary Conflicts, which examines the tangible dimensions of security, including territorial disputes, resource distribution, and ongoing conflicts; (3) Immaterial or Diffuse Geographies, focusing on energy, data, cyberspace, digital technologies, and artificial intelligence; and (4) International Security Perspectives on Governance and International Law.

As such, the handbook brings together multiple aspects of international security, combining theories and case studies. While continuing to track the development of the new and diverse security concepts, it also considers the latest relevant international events or other important topics, such as energy security, maritime security, decarbonisation of global economy, armed conflict, populism, Ukraine War, Artificial Intelligence, Lethal Autonomous Weapons Systems (LAWS), Arctic, and Feminist Movements.

Francisco B. S. José Leandro (Portuguese, Macau resident) received his Ph.D. in Political Science and International Relations from the Catholic University of Portugal in 2010. From 2014 to 2018, he served as the Program Coordinator at the Institute of Social and Legal Studies, Faculty of Humanities, University of Saint Joseph in Macau, China. From 2018 to 2023, he was the Associate Dean of the Institute for Research on Portuguese-Speaking Countries at the City University of Macau, China. Currently, he is an Associate Professor with Habilitation in International Relations at the Faculty of Social Sciences, University of Macau, and Deputy Director of the Institute for Global and Public Affairs. His recent publications include: The Palgrave Handbook of Globalization with Chinese Characteristics (2023), Palgrave Macmillan; Changing the Paradigm of Energy Geopolitics: Resources and Pathways in the Light of Global Climate Challenges (2023), Peter Lang Publishers; Portuguese-speaking Small Island Developing States: The Development Journeys of Cabo Verde, São Tomé and Príncipe, and Timor-Leste (2023), Palgrave Macmillan; The Palgrave Handbook on China-Europe-Africa Relations (2024), Palgrave Macmillan; and Is China a Global Power? The Three Great Walls of the Middle Kingdom (2025), Palgrave Macmillan. Francisco Leandro is a member of CEI ISCTE and OBSERVARE (Observatory of Foreign Relations), a research centre for International Relations established in 1996 at the Autonomous University of Lisbon, Portugal. In 2026, he was awarded the Senior Fellow of Advance HE (SFHEA) accreditation (Number PR530307).

Laura C. Ferreira-Pereira (Portuguese) received her PhD in International Relations from the University of Kent at Canterbury (UK). She is Full Professor of Political Science and International Relations of the University of Minho where she teaches various courses at both graduate and postgraduate level, and conducts research in the domains of International Relations and European Union Studies. She is integrated member of the Research Centre in Political Science (CICP-UMinho) of the same university; and Visiting Professor of the University of São Paulo, since 2012. Laura Ferreira-Pereira is the editor of Portugal in the European Union (Routledge, 2014) and co-editor of The European Union’s Strategic Partnerships (Palgrave Macmillan, 2021, with Michael Smith). She has acted as guest editor of Special Issues published in Journal of Contemporary European Studies (2023), Cambridge Review of International Affairs (2016) and European Security (2012). She is also contributor to other leading journals, such as Journal of Common Market Studies, Democratization, Cooperation and Conflict, Journal of European Integration, Contemporary Politics, and International Politics; and has published in several edited volumes. Her current research explores the EU’s strategic partnership diplomacy and relations with the Lusophone world; Europeanisation within and beyond Europe; comparative regional integration (with an emphasis on security and defence); Brexit and small states; China in global affairs and Luso-Chinese relations. Laura Ferreira-Pereira is a member of the editorial boards of the journals Contemporary Politics, Journal of Contemporary European Studies, Global Society, and Revista Brasileira de Política Internacional. She is a founding member of the European International Studies Association (EISA).

Luís Tome (Portuguese) is Full Professor at the Autónoma University of Lisbon / Universidade Autónoma de Lisboa (UAL), where he serves as Director of the Department of International Relations and of its research unit OBSERVARE – Observatory of Foreign Relations. He is also a Researcher at the Portuguese Institute of International Relations at Universidade Nova de Lisboa (IPRI-NOVA). He has been a visiting professor at the Portuguese National Defence Institute (IDN), the Military University Institute (IUM), and the Higher Institute of Police Sciences and Internal Security (ISCPSI), as also at La Sapienza University of Rome-Italy, the Middle East Technical University (METU) in Ankara-Turkey and the University of Macau-China, among other institutions in Europe, Brazil, Angola, and East Timor. He was Special Adviser for International Relations and Counter-Terrorism in the Office of the Minister of Internal Affairs (Nov. 2015 – Oct. 2017), Special Adviser to the Vice-President of the European Parliament (1999-2004), and NATO Researcher for two years, authoring the report “Russia and NATO’s Enlargement” (2000). Professor Luis Tomé's research focuses on International Relations, Geopolitics, and Security Studies, with particular expertise in the Euro-Atlantic, Eurasian, and Asia-Pacific regions. He is the author and co-author of more than a dozen books, as well as numerous essays and articles published in leading academic journals. He frequently speaks at high-level international conferences and regularly collaborates with the media as a commentator on international politics and security issues. He holds a BA in International Relations from the Autónoma University of Lisbon (UAL), an MA in Strategy from the Higher Institute of Social and Political Sciences (ISCSP) of the University of Lisbon, and a PhD in International Relations from the Faculty of Economics of the University of Coimbra (FEUC).

Yichao Li (Chinese) received her Ph.D. degree from the Institute for Research on Portuguese-speaking Countries, City University of Macau (China) in 2021. She also received a Master’s degree in comparative civil law (in Chinese) from the University of Macau (China) in 2018. From 2021 to 2022, she has been a postdoctoral researcher at the Centre for International Studies, ISCTE-IUL, Lisbon, Portugal. Since 2023, she is currently an assistant research fellow at Institute of African Studies, Zhejiang Normal University, China. Her current research interests are the Belt and Road Initiative, Portuguese-speaking countries, and Sino-African relations. Her latest publication stands as: Li, Y., Leandro, F., da Silva, J. T., & Rodrigues, C. (eds.). (2025). The Palgrave Handbook on China-Europe-Africa Relations: Legacies and the New International Order. Palgrave MacMillan. Costa, C. M., & Li, Y. (2025). Evolving Africa–EU Relations: Changes in Discourse from the Cotonou Agreement to the Samoa Agreement. Canadian Journal of African Studies / Revue canadienne des études africaines.