In recent years, the European security environment has been subjected to many tests. For the first time since the end of the Second World War, Europe is struggling with new, hitherto unknown threats and challenges in the area of security. Today’s security environment is increasingly volatile, complex and uncertain. At the same time, there is a deficit of its understanding, which results, among others, from its interdisciplinarity and multifaceted nature, as well as the penetration of many military factors and civilian, the development of new technologies, as well as globalization processes and their consequences. An additional factor intensifying the perception of changes in the security environment is the reduction of time spent on analyzing and understanding the changes taking place, as well as planning and implementing adequate solutions. In this context, the situation on NATO’s eastern flank is becoming one of the key issues to ensure the security of this part of Europe. Due to its international obligations resulting from its accession to the EU and the Schengen Agreement, Poland has assumed the obligation to ensure the security and inviolability of the Polish eastern border, which is integral with the external border of the European Union and NATO. Actions and efforts in the field of security, however, depend not only on the defense system of a given country, but on many factors, including geopolitical, historical and military conditions. The events of the last two years in its immediate vicinity are also significant for Poland’s security, including the crisis on the Polish-Belarusian border and the war in Ukraine. The main purpose of these considerations is to try to find an answer to the question of how to ensure the security of the Polish eastern border in the current security environment.