Two miles to the south of the city is a wide, sandy stretch of ground, twenty miles long, through which runs the Hun River, which can be forded almost anywhere. This approach to Mukden, forming the Russian center, was strongly held with sand-bag batteries. On the west of the town the very high railway embankment, running north and south of the river for many miles, was used to protect Mukden against attack from the west. The most vulnerable point in this line was the bridge over the Hun River, against which the Japanese delivered incessant attack. Mukden was strongly fortified by General Kuropatkin. The fortifications extended for nine miles, with forts and redoubts at intervals of a mile. The redoubts were all cleverly masked, and the line of fortification was protected by deep ditches and pits, all with stakes at the bottom, by wire entanglements, land mines, and a line of felled trees. [Sidenote: Betwixt Winter and Spring] Winter still howls over Manchuria when February is drawing to a close, but the early days of March, just as through the central United States, bring the first flush of spring. The ground remains locked in the grip of a frost that turns earth to steel to a depth of seven feet. The rivers are still securely ice-bound, but overhead the sun begins a mastery over the overpowering cold. If the nights remain bitterly cold, the days are increasingly warm and throughout the daylight hours conditions are ideal for the work of the soldier. The weather, therefore, fairly trumpeted a call to arms to the two vast armies that confronted each other south of the Sha-ho River. The earliest moves were made over whitened plains with snow storms still driving over hills and plain out of the bleak north. Marshal Oyama, the Japanese commander, evidently realized that the struggle would be long and, indeed, before its end winter had, in fact, given place to the opening days of spring. The advantages were many. The movement of artillery was facilitated by the hard surface of frozen ground and the ease with which ice-covered streams and rivers could be crossed. Lack of foliage deprived the army of the protection that so greatly aided the advance on Liao-yang, and so effectively shielded the artillery in that struggle. The broken nature of the country, the heavy calibre guns, firing from one to five miles with accuracy, minimized the disadvantage of fighting over a bare land and if lack of protection of foliage and growing crops added to the Japanese losses it failed to check the vigor or relentlessness of the advance once it had begun. [Sidenote: The Line of Battle]