DARDANELLES (Turk. Bahr-Se f ed Boghazi), the strait (anciently called the Hellespont) that unites the Sea of Marmora with the Aegean. The city of Dardanus in the Troad, where Mithridates and Sulla signed a treaty in 84 B.c., gave the strait its name. The shores are formed by the peninsula of Gallipoli on the north-west and by Asia Minor on the south-east ; it ex tends for a distance of about 47m. with an average breadth of 3 or 4 miles. At the Aegean extremity stand the castles of Sedil Bahr and Kum Kaleh respectively in Europe and Asia; and near the Marmora extremity is the town of Gallipoli (Callipolis) on the northern shore, and that of Lamsaki or Lapsaki (Lampsacus) on the southern. The two most famous castles of the Dardanelles are Chanak-Kalehsi, Sultanieh-Kalehsi, or the Old Castle of Anatolia, and Kilid-Bahr, or the Old Castle of Rumelia. The strait has long been famous in history since the passage of Xerxes' army by a bridge of boats. It is the scene of the story of Hero and Leander, and of Byron's successful attempt to rival Leander. The strategic importance of the strait has always been very great, since it is the gateway to Constantinople and the Black Sea from the Mediterranean. Although easily capable of defence, the strait was forced by the English admiral, Sir J. T. Duckworth, in 1807; and during the World War a British sub marine under the command of Lieutenant-commander Stoker penetrated through the Turkish minefields and sank a Turkish battleship off the Golden Horn. Its strategic importance has given to it an international political importance that has found expression in what is known as the Straits (Dardanelles and Bosphorus) Question (q.v.). (I. F. D. M.)