This article explores the paradox of a globalized cooperative world that appears conducive to openness, yet simultaneously witnesses the proliferation of closed borders, physical barriers, and increased border militarization. The objective is to research, analyze, and categorize the various types of border militarization, offering both theoretical and practical perspectives. We propose new definitions for border militarization to encompass its diverse expressions, ranging from overt to subtle forms. This study focuses on border militarization within Europe, specifically in peripheral countries on the outer fringes of the European Union’s Schengen regime, employing a comparative case study methodology. It provides in-depth insights into two similar cases and practical militarization following the 2015-2016 European migration crisis in Croatia and Poland. While the research has limitations, including its eurocentric focus and limited generalizability, the conclusions shed light on post-migration crisis long-term effects in Europe and the growing phenomenon of subtle and covert border militarization.