The _Field railways_, mentioned on the previous page, constituted a network of, altogether, 250 miles of narrow-gauge railways built and operated by the Russian troops--either alone or with the help of Chinese labourers--and designed to act as subsidiary arteries of the broad-gauge Eastern Chinese Railway by (1) providing for the transport therefrom of troops and supplies to the front; (2) conveying guns and munitions to the siege batteries, and (3) bringing back the sick and wounded. Horses, ponies and mules were employed for traction purposes. Each of the three Russian armies in the field had its own group of narrow-gauge lines, and the lines themselves served a most useful purpose in a country of primitive roads and inadequate local means of transport. In one instance a broad-gauge branch line was built inland, during the course of the war, from the Eastern Chinese Railway for a distance of twenty-five miles. A depôt was set up at its terminus, and thence the supplies were conveyed to the troops by a series of narrow-gauge lines extending to every part of that particular section of the theatre of war. Construction of the narrow-gauge line serving the Second Army, and extending nineteen miles from a point on the Eastern Chinese Railway near to Port Arthur, necessitated the provision of six bridges and three embankments. Three lines, the building of which was begun in January, 1905, were siege lines specially designed to serve the positions taken up at Liao-yang; but all three were abandoned on the evacuation of Mukden, early in March. It was, however, subsequent to the retreat from Mukden that the greatest degree of energy in constructing narrow-gauge lines was shown by the Russians. In addition to the 250 miles brought into use, there was still another 100 miles completed; but these could not be operated owing to the inadequate supply of wagons--a supply reduced still further through seizures made by the Japanese. During the course of the war the traffic carried on these military narrow-gauge lines included over 58,000 tons of provisions, stores, etc., 75,132 sick and wounded, and 24,786 other troops.[50] For the carrying out of all this construction work, and, also, for the operation of the Manchurian and Ussuri railways, Russia had twenty-four companies of _Railway Troops_, the total force of which was estimated at 11,431. In the first part of the war she relied upon her six East Siberian Railway Battalions. As the work increased other Battalions were brought from European Russia.