The book explores the history of the Slavs of the period when they constituted ethnic and linguistic unity. The work covers a significant period of time - from I millennium BC., When the Slavs, having left the ancient European community, began an independent path of development, until the early Middle Ages inclusive, when Slavic unity in conditions of wide settlement and métisation with other peoples broke up, separate Slavic ethnic groups and languages ​ ​ began to form.