The article examines the causes and consequences of the concentration of Russian troops near the Afghan border during the Anglo-Boer War in December 1899 and January 1900. Until now, the prevailing view in historiography has been that this action was designed exclusively to achieve Russia’s objectives in Central Asia — putting pressure on Britain to obtain concessions in Persia and Afghanistan. Challenging traditional interpretations, the author reveals, on the basis of archival documents introduced into scientific circulation for the first time, the motives of the initiators of the action, Emperor Nicholas II and his Minister of War, A.N. Kuropatkin. The military demonstration was conceived as a way of supporting the Boer republics by creating difficulties for Britain. By strengthening the garrison at Kushka, Russia demonstrated its ability to quickly move its troops to the Afghan border, which could then be sent to British India. It warned Great Britain of its ability to create undesirable complications while British forces were busy suppressing the Boer resistance. Russia prevented Britain from sending large reinforcements from India to the South African theatre of war at a critical time for the British army in southern Africa. Although this demonstration did not lead to direct Russian intervention in the Anglo-Boer conflict, it contributed to a significant reduction in the transfer of troops from India to the South African theatre of war. The British government and military command in India were concerned about Russia’s actions. Fearing the opening of a second front, they not only failed to increase the number of troops sent from the region but reduced it sixfold. Britain had to compensate for the shortage of soldiers with volunteers from the metropole and other colonies, which attests to the effectiveness of Russia’s actions. Thus, Russia was the only power that deployed its army to assist the armed forces of the Boer republics in their confrontation with the British Empire.