Russian aggression against Ukraine in 2014 represents not only an attack on the sovereignty, territorial integrity, and peaceful development of one of the biggest neighbors of the European Union but also the extensive consequences for Europe as a whole. Last Ukrainian crisis actually questions the overall architecture, the rules and institutions of European security, which were built after the end of the Cold War, and reveals multiple vulnerabilities in many other areas of the European Union. This master thesis argues that the disunity of the common foreign policy, economic interdependence between the EU and Russia and European energy dependence on Russia restrict the EU to act effectively in the international crisis such as the Ukrainian one and result in negative economic consequences for the European Union itself as well as jeopardize its influence as an important actor on the international stage. The analysis of primary and secondary sources of these three areas - foreign policy, trade and energy - shows the consequences of the newly emerging changes in eastern Europe. The European Common Foreign and Security Policy has proven to be immature and inefficient, economic sanctions critical to the European economy, and the energy dependence on Russia emerged as an extremely dangerous problem that not only dictated the course of the crisis, especially negative one for the EU, but also showed how the European Union and its energy policy should change fundamentally. By contributing to the field of international relations and the area of European public policy, this paper attempts to shed light on one of the biggest crisis on European soil in the post-bipolar order, and point out the fundamental limitations that brought the European Union in an unenviable position in relations with the unpredictable Russia.