The Russian-Ukrainian war is a multidimensional conflict based on historical grievances, geopolitical realities, and disputed territorial identities. This chapter traces the complex development of Ukrainian-Russian relations from the founding of Kievan Rus’ through the Soviet era to Ukraine’s post-Soviet independence. The war has had a profound impact on global security, particularly in terms of NATO’s involvement and its strategic realignments. In addition, the conflict has triggered one of the largest displacement crises in Europe, highlighting vulnerabilities in migration management and exacerbating geopolitical tensions. By analyzing the interplay between historical narratives, modern geopolitical stakes, and the emerging migration crisis, the chapter highlights the need for comprehensive policy responses that address the humanitarian, political, and security challenges of war. Through this examination, the study contributes to a nuanced understanding of the shifting boundaries of migration and security and illustrates the far-reaching consequences of war for international relations and governance frameworks.