This article examines the role of General V.E. Borisov in the decision-making process at the Headquarters of the Supreme Commander of the Russian Army in 1915–1917. General Borisov was a friend of General M.V. Alekseyev, and their contemporaries often characterized him as an unofficial advisor to Alekseyev, especially in military matters. When in August 1915 general Alekseyev was appointed as the Chief of Staff of the Supreme Commander and arrived at the Stavka in Mogilev, Borisov followed him, even though he did not have any official status at the time. Comparing the handwriting in Borisov's personal documents with the unsigned documents from the documents of Stavka, preserved at the Russian State Archive for Military History (RGVIA), this article concludes that Borisov in fact took part in the creation of several major notes on Russia's relations with the Allies in the Entente that laid the foundation for the Stavka’s strategic military decisions. In some cases he was the sole author of the documents, sometimes he wrote it together with Alekseyev. Borisov paid particular attention to Serbia and the Balkans, so this article analyses in detail the project of the allied offensive from Galicia and Salonika, developed by Borisov in November 1915. Confirmation of Borisov's participation in Stavka’s strategic activities improves our understanding of Stavka’s functioning and allows us to determine the ideological origins of the strategic decisions of the Russian high command, since, unlike General Alekseyev, Borisov left a vast theoretical legacy.