In Asia Minor progress was further barred by the watershed of the Euphrates and Tigris rivers to the south, and the Caucasian Mountains to the east. A practical way was found at the lower elevations of the Taurus and Amanus mountains--two parallel spurs which strike the sea at the Gulf of Alexandretta. This narrow neck of the bottle, as it were, is of enormous military importance alike to the Turks and to the British. Through it must pass any army of invasion by land from Europe or Asia Minor to Egypt or India; and, conversely, through it must pass any invading army from Mesopotamia into Asia Minor. If the British should conquer Mesopotamia and should intend to hold it--as they undoubtedly would--they will have no strategical frontiers until they secure the watershed of the Tigris and Euphrates rivers and the Taurus passage. If they secure the latter, Syria, Palestine, and Arabia will fall to them like apples off a tree. It would then be no longer necessary to defend the Suez Canal. The natural frontier of Egypt is the Taurus mountain range. Asia Minor is the real Turkey; the other portions of the empire--Mesopotamia, Syria, Palestine, Arabia, and Turkey in Europe--are only appendages. The eastern door into Asia Minor is Erzerum, and the southern door is the Taurus passage. Turkey can only part with these at the cost of her life. Russia has already captured Erzerum, and the British possess the Island of Cyprus, which commands the head of the Gulf of Alexandretta--twenty miles from the Taurus passage. That is, broadly, the situation. [Sidenote: Aleppo is the starting point of caravan routes.] Near the crossing of the Taurus and Amanus mountains lies the city of Aleppo, the starting-point for the overland caravan routes to Bagdad and India, and also to Damascus, Mecca, and Egypt. Just as surely as pioneer travelers always chose the easiest route, so the railways of to-day follow in their footsteps. The physical features of nature constrained both modern as well as ancient armies to travel the same way. Hence a railway map of the Balkans and of Asiatic Turkey is a first consideration in appreciating the strategical bearings of the Anglo-Russian campaign in Turkey-in-Asia, or the alleged rival Germanic-Turkish schemes for the invasion of Egypt, Persia, and India. Of no less importance is a knowledge of the available sea routes and inland rivers. [Sidenote: Bulgaria and Turkey depend on aid from Germany.] The ability of Bulgaria and Turkey to carry on the war depends on aid from Germany in men, munitions, and money. These allies are the weakest members of the Central Group, and may be the first to give in if circumstances are adverse to their adventure. [Sidenote: The importance of the Balkan railway.]