The main goal of this thesis was to explain one of the causes of the war in Ukraine. This research is different form the others because it approaches the problem from the angle of the relationship between two great powers. The paper explores the relationship between Russia and the West, two powerful actors, whose relationship culminated in the conflict in Ukraine. Thesis analyzes the events and situations that influenced changes in the relationship and detects crucial points in the development of their relationship. It was found that one of the main contentious points of the relationship is the different understanding of the interantional and security environment. The perceptions of both sides change and affect their behaviour and their relationship. Russian expectations of a common security framework have not been met. The West failed to integrate Russia, so Russia turned toother allies. Russia attacked Ukraine to show that it is ready to protect it's interests and draw a line in response to western unilateralism. The paper contributes by offering a fresh perspective and explanation of this conflict in a different way than a classical research. Thesis explains this conflict at the relationship level and documents it through the period from the creation of Russian Federation to the present day.