The dogged defence of the Dardanelles had convinced Germany that, granted proper support, Turkey could be depended upon to give a good account of herself. The problem was one of supplementing Ottoman man power with Teutonic military genius, technical skill, and organizing ability. The enlistment of Bulgaria and the obliteration of Serbia made possible more active German assistance to Turkey, and during the latter months of 1915 and the early months of 1916 strenuous efforts were made to bring the Turkish military machine to a high point of efficiency. Large numbers of German staff officers were despatched to Mesopotamia, Syria, and Anatolia, and Turkish officers were brought to the French and Russian fronts to learn the methods of modern warfare. The Prussian system of military service was adopted throughout the Ottoman Empire, and exemptions were reduced to a minimum. Liberal credits were established with German banks for the purchase of supplies for the new levies of troops. Field Marshal von der Goltz was sent to Mesopotamia as commander-in-chief of the Turkish troops in that region.[17] Perhaps the chief handicap of the Turks in all their campaigns was inadequate means of transportation. The Ottoman armies operating in the vicinity of Gaza and of Bagdad were dependent upon lines of communication more than twelve hundred miles long; and had the Bagdad Railway been non-existent, it is doubtful if any military operations at all could have been conducted in those regions. But the Bagdad Railway was uncompleted. Troops and supplies being despatched from or to Anatolia had to be transported across the Taurus and Amanus mountains by mule-back, wagon, or automobile, and then reloaded on cars south or north of the unfinished tunnels. To remedy these deficiencies, herculean efforts were made by Germans and Turks during 1915 to improve the service on existing lines and to hurry the completion of the Bagdad Railway. Locomotives and other rolling stock were shipped to Turkey, and German railway experts coöperated with the military authorities in utilizing transportation facilities to the best advantage. In September, 1915, the Bagtché tunnel was pierced; and although through service to Aleppo was not inaugurated until October, 1918, a temporary narrow-gauge line was used, during the interim, to transport troops and matériel through the tunnel. Commenting on the importance of the Bagtché tunnel, the American Consul General at Constantinople wrote: “With its completion the most serious difficulties connected with the construction of the Bagdad Railway have been overcome, and the work of connecting up many of the isolated stretches of track may be expected to be completed with reasonable rapidity. In spite of delays occasioned by the war, this most important undertaking in railway construction in Turkey has passed the problematical stage and is now certain to become an accomplished fact in the near future.”[18]