Here the first material point in the campaign showed the power of resistance that tradition and discipline yet maintained in the French army. The long resistance of Tournai and its small garrison largely determined what was to follow. Its siege had been undertaken in the hope of its rapid termination, which the exiguity of its garrison and the impossibility of its succour rendered probable. But though Marlborough had established his headquarters before the place by the evening of the 27th of June, and Eugene upon the next day, the 28th, though trenches were opened in the first week of July and the first of the heavy fighting began upon the 8th of that month, though the town itself was occupied after a fortnight's struggle, yet it was not until the 3rd of September that the citadel surrendered. This protracted resistance largely determined what was to follow. While it lasted no action could be undertaken against Villars. Meanwhile the French forces were growing stronger, and, most important of all, the first results of the harvest began to be felt. Tournai once taken, it was the business of the allies to pierce the French line of defence as soon as possible, and with that object to bring Villars to battle and to defeat him. The plan chosen for this object was as follows:-- The allied army to march to the extreme right of the positions which the French could hope to defend. There the allies would contain the little garrison of Mons. Thither the mass of the French forces must march in order to bar the enemy's advance upon Paris, and upon some point near Mons the whole weight of the allies could fall upon them, destroy them, and leave the way to the capital open. [Illustration: Sketch Map showing how the Lines of La Bassée blocked the advance of the Allies on Paris, and Marlborough's plan for turning them by the successive capture of Tournai and Mons.] The plan was strategically wise. The lines of La Bassée proper could not be pierced, but this right extremity of the French positions was backed by easy country; the swamps, canals, and entrenchments of the main line to the north and west were absent. With the defeat of the inferior French forces at this point all obstacle to an advance into the heart of France would be removed.