The book of academician M.N. Tikhomirov, offered to the attention of readers, is devoted to an important and interesting issue - the accession of Mern to Russia. The study of this issue is of great importance for the development of the history of our multinational Motherland. Based on extensive and diverse sources - unpublished documents of state archives, memoirs of contemporaries of the event and other materials - academician M.N. Tikhomirov describes the development of economic and political ties between Russia and Turkmenistan until the 70s of the XIX century, the accession of Akhal Tekinsky and Mervsky (Mari) oases, and also talks about the situation of the Trans-Caspian region at the end of the XIX century.