Marshal Oyama's problem, as has been said, was to envelope the Russian armies. It was as though the Russian triangle were a bottle into which a cork must be driven. On the neck of the bottle, ten miles apart, are Mukden, on the West, and Fushan, on the east. Between these points the Russians would be compelled to disgorge in a retreat northward should the center be broken and a retreat became necessary. Here, then, was the Japanese objective. To take Mukden and Fushan, to drive the forces there southward toward the Sha-ho, and to place a force northward to be the cork in the bottle, driving back the retreat on the advance of the center, right and left armies, thus surrounding the Russians with a hoop of men and guns that would make escape or victory impossible. Thus it is that a battle that centered twenty-five miles southward on the Sha-ho River becomes officially known as the battle of Mukden, for here centered the really vital struggle of the whole memorable engagement. The Russian line of communication centers at Harbin, where the railroad which pierces Manchuria and the Liao-tung Peninsula to Port Arthur, branches southward from the Siberian railroad, the artery through which flows life from St. Petersburg and European Russia to the Far Eastern armies. The whole Manchurian campaign has moved northward along this railroad, the salvation of the Russian army always depending on its ability to keep open at its rear this means of sustenance, of ammunition supply, of reinforcement supply, of transport of every kind, whether advancing or retreating. The railroad reached the actual Russian lines just west of Mukden and then continued southward to the Sha-ho, branching here and there to various field depots convenient to the various army units. Marshal Oyama's plan of battle comprehended, as its greatest achievement, the cutting of this railroad north of Mukden before a retreat could be made. This was the first and most vital contribution if the ultimate plan to envelop the Russians was to succeed. This plan failed and hence the prize of decisive, final victory slipped from the grasp of the Japanese commander, however great the blow he dealt to the Russian army. [Sidenote: Russian Flanks Strongly Protected]