Russian annals had a centuries-old history by the beginning of the 15th century. It arose in the heyday of Kievan Rus, when the Russian state was united and mighty. The history of Russia of the Kyiv period is set out in the initial Russian annals, known as the "Tale of Bygone Years." "The Tale of Bygone Years" talked about the origin of the Slavs and the Slavic language, about the formation of the Russian state, its geography, international relations, the campaigns of the Russian princes to Constantinople and the struggle of the Russian people with the steppe nomads. The first Russian chroniclers surveyed the entire Russian land from the Baltic to the Black Sea, from Galich South to the White Lake and wrote about its fate. They entered both oral traditions and records of earlier years on the pages of annals, used Byzantine, Bulgarian, Czech and Polish sources.