Baghdad Railway, major rail line connecting Istanbul with the Persian Gulf region. Work on the first phase of the railway, which involved an extension of an existing line between Haidar Pasha and Ismid to Ankara, was begun in 1888 by the Ottoman Empire with German financial assistance. In 1902 the Ottoman government granted a German firm the concession to lay new track eastward from Ankara to Baghdad. Financial difficulties and the technical problems of tunneling through the Taurus Mountains made progress extremely slow. Because of its potential strategic importance, work on the line was accelerated after the empire entered World War I on the side of Germany and the other Central Powers. By the end of the war in 1918 the line had been extended from the Bosporus to Nusaybin, several hundred miles short of Baghdad. This remaining stretch and a subsequent extension to the port of Basra near the Persian Gulf were eventually completed by Syria and Iraq, which had been formed after the dismemberment of the Ottoman Empire.