The analysis presented to the readers is based on an in-depth study of the content contained in the acts and documents of the European Union and concerning the implementation of the EU strategy in the field of security union in the context of the war in Ukraine. The text justifies and proves that the European Union has taken strategic decisions and actions providing Ukraine with strong support for the general cause economic, military, social and financial resilience, including granting its humanitarian aid. In addition, the EU strongly condemned Russia’s indiscriminate attacks against civilians and civilian infrastructure and called on Russia to immediately and unconditionally withdraw all troops and military equipment from all of Ukraine’s territory within its internationally recognized borders. The analysis of the research material presented in the study led to the formulation of the main hypothesis, which is: the war in Ukraine strengthens the EU at the strategic level at the same time leading to a clash of diverse forces and interests, which may result in fragmentation of the system, and thus its local (sectoral) weakening.