The German plan was to abandon the mere passive defence of their frontiers, assume the offensive, and strike a blow directly against Warsaw and the group of fortresses beyond the Vistula that form the citadel of the Russian power in Poland. The German armies were to advance from the borders of the provinces of Posen and Silesia in a converging march upon Warsaw. The left column from Thorn was to advance along the south bank of the great bend of the Vistula which runs north-westward from Novo Gorgievsk by Plock. The central column from the Posen frontier was to march on Lowicz and the great factory town of Lodz--after Warsaw the largest place in Poland--the third column, which had already occupied Czenstochowa, just inside the Russian frontier towards Silesia, was to protect the flank of the advance and march on the Vistula in the direction of Ivangorod. A fourth column was to march on Kielce, forming the link with an Austrian advance through Northern Galicia towards the river San, which was intended to reoccupy Jaroslav and raise the siege of Przemysl. The country through which the line of advance lay was the undulating Polish plain, a district with many clumps and belts of forest, and almost destitute of good roads. Once the weather broke, at the end of autumn, much of the ground would be reduced to a marshy condition that would make it impassable until the first frost of winter hardened it again. The German Staff hoped to carry through the campaign while the region was everywhere practicable, and, even if Warsaw were not captured, to make the Vistula their line of defence, where, having secured the railways behind them, they might hope to hold their own on a front shorter by many hundred miles than the long curving frontier of their own territory. It was expected that the first movement into the Polish plain would have the result of forcing the enemy not only to abandon the advance already begun towards Cracow, but to evacuate a considerable part of the ground they had overrun in Galicia, and at the same time to withdraw some of their forces from the East Prussian border. German reports went to show that the enemy had no large forces in the country between the middle Vistula and the Posen-Thorn frontier. The first stage of the German advance would, therefore, not be likely to meet with any very serious opposition.