This presentation explores the historical and religious roots of Eastern Europe, with a particular focus on relations between Russia and Ukraine. To understand the current situation and lay the foundations for dialogue, it is necessary to take a long-term perspective. This perspective should consider the complex religious and cultural history of the Eastern Slavic world, which in modern times is deeply intertwined with the development of different national identities. Firstly, it should be remembered that the process of acculturation of the Slavic world to Christianity took place when the traditions of Rome and Constantinople diverged significantly. While Rus' became part of the Slavic Byzantine world as early as the 10th century, the Tatar invasion of the 13th century caused its fragmentation, favoring different orientations. Between the 15th and 17th centuries, the Ruthenian lands, linked to the Polish-Lithuanian Respublica, experienced a cultural and religious renaissance. On the one hand, the Union of Brest (1596) gave rise to an Eastern Church united with Rome, while on the other, ecclesiastical figures such as Petro Mohyla renewed Kiev Orthodoxy under the aegis of Constantinople, integrating scholastic models and contributing to the formation of a Ukrainian cultural identity. With the rise of the Russian Empire, Moscow gained direct control over the metropolis of Kyiv (1686) and initiated a process of centralization and standardization, which tended to suppress local particularities. The tension between the preservation of different cultural and religious traditions and imperial pressures remains underlying in the contemporary era, when the history of the European continent is marked by the development of different national identities. These tensions continue to weigh heavily today, revealing their religious origins.