Answer based on context:

The Ottoman Empire often treated POWs poorly. Some 11,800 British Empire soldiers, most of them Indians, became prisoners after the Siege of Kut in Mesopotamia in April 1916; 4,250 died in captivity. Although many were in a poor condition when captured, Ottoman officers forced them to march 1,100 kilometres  to Anatolia. A survivor said: "We were driven along like beasts; to drop out was to die." The survivors were then forced to build a railway through the Taurus Mountains. In Russia, when the prisoners from the Czech Legion of the Austro-Hungarian army were released in 1917, they re-armed themselves and briefly became a military and diplomatic force during the Russian Civil War. While the Allied prisoners of the Central Powers were quickly sent home at the end of active hostilities, the same treatment was not granted to Central Power prisoners of the Allies and Russia, many of whom served as forced labour, e.g., in France until 1920. They were released only after many approaches by the Red Cross to the Allied Supreme Council. German prisoners were still being held in Russia as late as 1924.

Who built a railway through the Taurus Mountains?
British Empire soldiers