The Bosphorus is one of the most coveted sea routes in the world, possibly rivaled in importance only by the Panama and Suez Canals. Unlike the latter two, the Bosphorus is an entirely natural waterway, linking the Black Sea to the Sea of Marmara and thence via the Dardanelles to the Mediterranean. It was the site of Byzantine Constantinople and, after 1453, Ottoman Istanbul. The Bosphorus divides Istanbul into European and Asian sections, making Istanbul the only city in the world to straddle two continents.
Ever since the expansion of Russian power starting in had the reign of Peter the Great (r. 1682–1725), the Russian Empire had sought control of the Black Sea straits, the Bosphorus and the Dardanelles. As the Russian Empire became the dominant power in the Black Sea, Russia's rulers became obsessed with control of the straits in order to give the Russian fleet access to the warm waters of the Mediterranean. This was the root of the so-called Eastern Question, which so dominated international diplomacy in the nineteenth century. The basic assumption in the Eastern Question, which turned out to be false, was that the Ottoman Empire could collapse at any moment and that it was vital for Britain and France to deny Russia control of the Bosphorus. In a sense the Bosphorus was the eye of the storm in the high politics of the belle epoque.
Nor was Russia alone in coveting the Bosphorus. The ultimate aim of Napoleon Bonaparte's Egyptian expedition was to march through Asiatic Turkey, conquer Istanbul, and set it up as the capital of his "Empire in the Orient," thus controlling the Bosphorus and denying it to Russia.
As the economy of the Russian Empire became more and more intertwined with that of Europe, exports of Russian foodstuffs, particularly wheat, became a major factor in the fate of the Bosphorus. With the advent of steam and railways the importance of this strategic seaway increased as regular steamship services started up between major Black Sea ports, such as Odessa and Varna, and Europe. Accordingly, control of the Bosphorus became the number one foreign policy goal of the Russian Empire. In 1833, in return for backing against the sultan's rebellious vassal Muhammad Ali of Egypt, the Russians secured the Treaty of Unkiar Skelessi, which granted the Russians extensive rights on the Bosphorus, tantamount to joint control with the Ottoman Empire. For the first and only time, a Russian army and navy were invited into Ottoman territory by Sultan Mahmud II (r. 1808–1839). The Russian navy sailed into the Bosphorus, and Russian troops encamped on its hills. The treaty was abrogated in 1841 by the Straits Convention, which again greatly curtailed Russian influence and basically enabled the Ottomans to close down the straits at times of war. The principle of international law that in times of peace the Bosphorus would be closed to all ships of war was first established in the Treaty of the Dardanelles (1809) between Britain and the Ottoman Empire.
The Crimean War (1853–1856) was fought largely as a war for the control of the Bosphorus. For the first time in modern warfare the Ottomans fought alongside two great-power allies, Britain and France. Florence Nightingale, the mother of modern nursing, became world famous for her care of the war wounded in her hospital barracks, the Selimiye, overlooking the Bosphorus and the Golden Horn. Mark Twain wrote extensively and pejoratively on what he saw of the city and the Bosphorus in The Innocents Abroad (1869), becoming the first American journalist to write extensively on the city.
The Bosphorus was salient in the run-up to World War I in the Balkans. After the Young Turk takeover of power in 1908, the Ottoman Empire moved closer to Germany as the war approached. Defense of the straits became a priority issue for the Ottoman state. The Germans supplied extensive weaponry, such as powerful shore batteries, that proved decisive in World War I, particularly during the Gallipoli campaign. On 11 August 1914 the Ottoman Empire allowed safe passage through the straits to two German battle cruisers, the Goeben and the Breslau, which were handed over to the Ottoman Empire in a fictitious sale. On 30 October the two ships, flying Ottoman flags but manned by German crews, exited the Bosphorus and bombarded Russian ports, in effect bringing the Ottoman Empire into World War I.
Anderson, M. S. The Eastern Question, 1774–1923: A Study in International Relations. London, 1966.
Kent, Marian, ed. The Great Powers and the End of the Ottoman Empire. 2nd ed. London, 1996.
King, Charles. The Black Sea: A History. Oxford, U.K., 2004.
Shaw, Stanford J., and Ezel Kural Shaw. History of the Ottoman Empire and Modern Turkey. 2 vols. Cambridge, U.K., 1976–1977.