The Constantinople Agreement (also known as the Straits Agreement) comprised a secret exchange of diplomatic correspondence between members of the Triple Entente from 4 March to 10 April, 1915 during World War I. France and Great Britain promised to give Constantinople and the Dardanelles (which at the time were part of the Ottoman Empire) to the Russian Empire in the event of victory. Britain and France put forward their own claims, to an increased sphere of influence in Iran in the case of Britain and to annexation of Syria (including Palestine) and Cilicia for France, all sides also agreeing that the governance of the Holy Places and Arabia would be under independent Muslim rule. The Greek government was neutral, but in 1915 it negotiated with the Allies, offering soldiers and especially a geographical launching point for attacks on the Turkish Straits. Greece itself wanted control of Constantinople. Russia vetoed the Greek proposal, because its main war goal was to control the Straits, and take control of Constantinople.
Though the Allied attempt to seize the area in the Gallipoli Campaign failed, Constantinople was nevertheless occupied by the victorious Allies at the end of the war in 1918. By that time, however, the Russian Revolution had brought about Russian withdrawal from the war, and as it was no longer one of the Allied Powers the agreement was not implemented. Its existence had been revealed by the Bolshevik government in 1917.
Access to the Turkish Straits was governed by the 1841 London Straits Convention which stipulated the closure of the straits to warships and, after the Crimean War, by the Treaty of Paris (1856) which made universal the principle of commercial freedom at the same time as forbidding any militarization in and around the Black Sea, later amended by the Treaty of London (1871) and reaffirmed in the Treaty of Berlin (1878).
In early 1907, in the talks leading up to the Anglo-Russian Convention, Count Alexander Izvolsky, then Russian Minister of Foreign Affairs, raised the question of the Straits and talks were carried on in London through the Russian ambassador, Count Alexander Benckendorff. Little is known but the "suggestion appears to have been made that Russia should have free egress from the Black Sea through the Straits, while other powers should have the right to send their vessels of war into the Straits without going into the Black Sea" together with some talk of "Russia's occupying the Bosphorus and England the Dardanelles, after which the Straits might be opened to other warships as well." In the event nothing came of the discussions at the time.
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."
Alexander Izvolsky, the Russian Foreign Minister, in the latter part of 1908 was able to get conditional support for a change in the Straits regime from Austro-Hungarian Foreign Minister Alois Lexa von Aehrenthal, Italian Minister of Foreign Affairs Tommaso Tittoni and the German Ambassador to Paris, Wilhelm von Schoen as well as from Secretary of State for Foreign Affairs Sir Edward Grey, the latter on 14 October, 1908, being clearest on the subject while at the same time indicating that Turkish agreement was a prerequisite.
During the Bosnian Crisis of 1908, in the Italo-Turkish War of 1911/12 as well as during the Balkan Wars of 1912/13, Russia made attempts to obtain the opening of the straits for Russian warships but failed for want of support from the Great powers. In April/May of 1912, the straits were closed for some weeks and in response to subsequent threats of closure, Russia indicated that it would take action in the event of a prolonged closure.
At the outbreak of war, the Ottoman Empire was diplomatically isolated; it had sought alliance with Britain at the end of 1911 and between May and July 1914 with France, Russia and on 22 July with Germany, to no avail. 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. On 30 July, Russian Minister of Foreign Affairs Sergey Sazonov instructed Benckendorff:
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".
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 as of November 1914 and it's genesis as being earlier in September , prior to the Ottoman entry into the war.
From 4 March to 10 April 1915, the Triple Entente (Britain, France, and Russia) secretly discussed how to divide up the lands of the Ottoman Empire. Britain was to control an even larger zone in Iran while Russia would get the Ottoman capital, Constantinople. The Dardanelles were also promised to Russia. The language of the agreement described the following boundaries:
Even though the British and the French sought to limit Russian claims, they 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 agreement was one of a series of agreements regarding the partition of the Ottoman Empire by the Triple Entente and Italy following the war, including the Treaty of London (1915), the Sykes–Picot Agreement (1916) and the Agreement of Saint-Jean-de-Maurienne (April to August 1917).
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. By that time, the Communist Bolsheviks had seized power in Russian during the October Revolution of 1917 and had signed a separate peace with the Central Powers in March 1918, dropping out of the war. As the Allies therefore no longer considered Russia among their number, and, indeed, did not even recognise the legitimacy of the Bolshevik government, the agreement was never implemented.
- Fitzgerald, Edward Peter. "France's Middle Eastern Ambitions, the Sykes–Picot Negotiations, and the Oil Fields of Mosul." The Journal of Modern History 66.4 (1994): 697–725. JSTOR 2125155
- Fromkin, David. A Peace to End All Peace. N.p.: Henry Holt & Company, Incorporated, 2001. Print.
- Helmreich, Paul C. "Italy and the Anglo-French Repudiation of the 1917 St. Jean de Maurienne Agreement." The Journal of Modern HIstory 48.2 (1976): 99–139. JSTOR 1877819
- Pınar Üre: Constantinople Agreement, in: 1914-1918-online. International Encyclopedia of the First World War.
- Hamilton, Richard F.; Herwig, Holger H. (2005). Decisions for War,1914–1917. Cambridge: Cambridge University Press. ISBN 978-0-51119-678-2.
- Renzi, William A. (March 1970). "Great Britain, Russia, and the Straits, 1914–1915". The Journal of Modern History. 42 (1): 2–20. doi:10.1086/240513. JSTOR 1905979.
- Bobroff, Ronald (24 February 2006). Roads to Glory: Late Imperial Russia and the Turkish Straits. I.B.Tauris. ISBN 978-1-84511-142-7.
- Smith, C.Jay (July 1965). "Great Britain and the 1914–1915 Straits Agreement with Russia: The British Promise of November 1914". American Historical Review. 70 (4): 1015–1034. doi:10.2307/1846901. JSTOR 1846901.
- Macfie, A.L. (1981). "The Straits Question,1908–1914". Political Science Quarterly. 22 (2): 321–332. Retrieved 10 October 2019.
- Macfie, A.L. (6 December 2006). "The straits question in the First World War, 1914–18". Middle Eastern Studies. 19 (1): 43–74. doi:10.1080/00263208308700533. JSTOR 1905979.
- Macfie, A.L (1998). The end of the Ottoman Empire, 1908–1923. Longman. ISBN 978-0-582-28763-1.
- Langer, William L. (January 1929). "Russia, the Straits Question, and the European Powers, 1904-8". The English Historical Review. 44 (173): 59–85. JSTOR 552495.
- Langer, William L. (September 1928). "Russia, the Straits Question and the Origins of the Balkan League, 1908–1912". Political Science Quarterly. 43 (3): 321–363. doi:10.2307/2142971. JSTOR 2142971.
- Kerner, Robert J. (September 1929). "Russia, the Straits, and Constantinople, 1914-15". The Journal of Modern History. 1 (3): 400–415. doi:10.1086/235488. JSTOR 1871427.
- Hurewitz, J.C. (July 1962). "Russia and the Turkish Straits: A Revaluation of the Origins of the Problem". World Politics. 14 (4): 605–632. doi:10.2307/2009311. JSTOR 2009311.
- Yıldız, Gültekin (July 1962). "How to Defend the Turkish Straits Against the Russians: A century-long 'Eastern Question' in British defence planning, 1815–1914". The Mariner's Mirror the International Quarterly Journal of the Society for Nautical Research. 105 (1): 40–59. doi:10.1080/00253359.2019.1565339.
- Likharev, Dmitrii V. (June 11, 2019). "Constantinople and the Black Sea straits as Russia's war aims in 1914–1917: A comparison of Russian and American interpretations". the Historian. 81 (2): 260–281. Retrieved 15 October 2019.