EUROPEAN SECURITY WITHOUT THE UNITED STATES: CHALLENGES AND PROSPECTS IN THE CONTEXT OF RUSSIAN AGGRESSION AGAINST UKRAINE

Abstract

Background. The European security architecture is undergoing a phase of structural transformation that will shape the future of the continent for decades to come. Europe is facing the most serious security challenge of the 21st century, while the role of the United States as a key ally is no longer unquestionable.

The relevance of this article is driven by the ongoing military aggression of the Russian Federation against Ukraine, as well as by the new approaches of the administration of U.S. President Donald Trump to the country’s role in guaranteeing security in Europe. Under these conditions, the effectiveness of the EU in implementing new security initiatives and mechanisms becomes a decisive factor for deterring Russia and protecting the EU’s eastern borders.

The purpose of this article is to analyse the current state of European security architecture and to trace the development of defence cooperation on the continent in the context of Russia’s ongoing aggression against Ukraine and the changing foreign policy priorities of the United States.

Methods. The research employs methods of systemic and structural-functional analysis, as well as comparative and historical-political approaches.

Results. The research demonstrates that in recent years the European Union has significantly intensified efforts to strengthen its own defence capabilities and deepen integration in the field of security and defence. The leadership of the EU and key Member States take seriously the publicly expressed intentions of the Trump administration regarding a reduction of the U.S. military presence in Europe. Since 2025, fundamentally new mechanisms of defence cooperation at the pan-European level have been established, with Ukraine actively involved in these initiatives. At the same time, U.S. security guarantees ‒ primarily nuclear ‒ continue to remain a defining factor of the European security architecture.

Conclusions. Russia’s aggression against Ukraine and U.S. foreign policy under the presidency of Donald Trump have posed a serious challenge to the European Union, highlighting the priority of strengthening its own defence capabilities. A significant increase in investments in the defence industry, the creation of new defence initiatives, and the active involvement of Ukraine in joint defence projects demonstrate that European states recognise the seriousness of security risks and the need to act proactively to ensure effective deterrence of potential Russian aggression against EU Member States.