The article introduces a little-known source into research paradigm. It is connected with the history of a great popular movement in Russia at the beginning of the 18th century - Bulavin uprising. It is referred to the Don Host Letter to Hassan Pasha, muhafiz (commandant) of the Ottoman fortress Achuev (Atchu) in the Kuban region. The origin of the document, key facts and dates are examined. The history of the Don Host Letter is presented against the other similar documents which compose one consolidated documentary complex. This refers to the letters to Kubanian mursa Sartlan and to Kuban Cossacks. These are original documents of the early 18th century, not delivered to addressees and picked up by the Russian authorities in May of 1708. Today all these document are kept in the Russian State Archive of Ancient Acts in Moscow. Correspondence of ataman K.А. Bulavin and Hassan Pasha and other addressees is considered in relation to reconstruction of the ataman’s strategic plans as well as input of the army archive. The article studies the heuristic potential of the document published in relation to relevant issues of Bulavin uprising history, external links of the Don Host, organization of the military records management. Having become the military ataman in May 1708, K.A. Bulavin tried to establish good-neighborly relations with Hassan Pasha and to get him interested in the development of trade relations and joint struggle against the Kalmyks. Correspondence with the Achuev commandant, among other examples, testifies to the restoration of the Don Host right to independent external contacts, substantially restricted in 1671.