Constantinople Agreement

[5] On 12 October 1908, the Russian Ambassador to France, Aleksandr Nelidov in a conversation with the British Ambassador to France, Lord Bertie, said that since Japan would not allow Russia to keep a Pacific fleet, and since the Baltic was practically closed throughout the winter, it was essential for Russia that the Black Sea should be made "the home for the Russian fleet whence she can move to the Mediterranean, the Baltic and the Far East as necessity may require.

[11] Russia was concerned about the potential arrival in the Black Sea of two modern warships being built by British shipyards for the Ottoman Navy, the Sultân Osmân-ı Evvel, which had been completed and was making preparations to leave, and the Reşadiye.

"First Lord of the Admiralty Winston Churchill had by then already decided on requisition and when the Turkish ambassador protested on 1 August, he was informed that "in view of the serious situation abroad it was not possible to allow a battleship to leave these waters and pass into the hands of a foreign buyer".

[13][c] Historian Dmitrii Likharev, analysing key contributions in the historiography of the subject points to contributions of C. Jay Smith who obtained access to the Asquith papers in the 1960s and to William Renzi in 1970 who made use of records released by the British National Archives to date Britain's promise of Constantinople to the Russians to November 1914 [d] and its genesis to earlier in September [e], prior to the Ottoman entry into the war.

The language of the agreement described the following boundaries: ...the city of Constantinople, the western bank of the Bosphorus, of the Sea of Marmara and of the Dardanelles, as well as southern Thrace to the Enez-Midye line... and... that part of the Asiatic shore that lies between the Bosphorus, the Sakarya River and a point to be determined on the Gulf of Izmit, and the islands of the Sea of Marmara, the Imbros and Tenedos islands.The British and the French sought to limit Russian claims, but were not able to do so, and also had to contend with the possibility that Russia might make a separate peace with the Central Powers.

The British Gallipoli Campaign (1915–16) was aimed at seizing the Dardanelles and Constantinople, but was defeated by the Ottomans, and the Allies did not gain control of the region until occupying it in November 1918, after the end of the war.