Tensions arose between Great Britain and Russia during the course of the Russo-Turkish War of 1977-78. Russia was gaining considerable influence in the Balkans and Great Britain recognized a threat to her interests. Britain became particularly alarmed with Russian actions in the Eastern Mediterranean which might impede British connections with India. In a letter of May 6, 1877, to Russia, Lord Berby reaffirmed the traditional British stance on Constantinople and the Straits, and included a polite warning to Russia against attempts to blockade the Suez Canal or to occupy Constantinople. When Russian troops moved westward, the British ordered portions of the fleet to sail to Besika Bay where they arrived on July 3, 1877.
The process of implementing the Russo-Turkish armistice, which had been signed January 31, 1878, exacerbated tensions between Britain and Russia. The British fleet set sail on February 8, for Mediterranean waters near Constantinople. Hostilities were avoided on February 18, 1878 when Russia agreed not to occupy Gallipoli and Britain agreed not to land troops on either side of the straits.
The signing of the Treaty of San Stefano on March 3, 1878 opened the possibilities of settling the Eastern Question through further negotiations at the Congress of Berlin. Preparations for this Congress led to the second period of heightened tensions between Russia and Great Britain. Domestic strife in England hindered decisive policy making on the Eastern Question. This was resolved in March 1878 when Salisbury replaced Lord Derby as Foreign Minister. On April 1, 1878 he distributed a circular which defended British policies and defined her position on the Eastern Question. Britain and Russia reached agreement on May 30. On July 13, a final agreement was signed at a congress in Berlin, with Bismarck assuming the role of mediator.