The Dardanelles
The Dardanelles is a 61 kilometres long, narrow strait of water. The Dardanelles have always been strategically important because they link the Black Sea with the Mediterranean Sea. At the time of World War I, the Dardanelles were controlled by the Ottoman Empire. Control of the Dardanelles and Bosporus straits by the Ottomans prevented the Russian fleet in the Black Sea from joining the Allied fleet in the Mediterranean. They also prevented the Mediterranean fleet from attacking Constantinople (present-day Istanbul), the Ottoman capital, located on the Sea of Marmara.
The voyage of AE2 in the Dardanelles
© Australian War Memorial
Natural and built defences
The Dardanelles are naturally difficult to negotiate as they resemble a twisted hourglass, and the notorious passage called the Narrows is easily defended from both shores. There are also two currents flowing through the Dardanelles: a surface freshwater current of 1 to 4 knots flowing towards the Aegean Sea, and an underwater current of salt water flowing towards the Sea of Marmara.
The Ottoman Empire added built defences to enhance the Dardanelles’ natural barriers.
By 1915, forts with heavy guns and mobile howitzers were strung along both sides of the mouth near the Aegean. From Kephez Point, the first turn before the Narrows, rows of mines were laid. The single line of mines secretly laid parallel to the Asia Minor coast had cut the Allied fleet apart on 18 March when it first tried to force the strait. Sweeping searchlights were ready to pick out any night attacker. (Brenchley, F & E 2001, Stoker’s Submarine, p 55)
The 
Australian War Memorial website argues that the Gallipoli landings were mounted in an attempt to take control of Ottoman forts and artillery along the Dardanelles’ shores.
