The great object of Louis and his generals had been to construct such a line of defences as might prevent the irruption of the enemy into the French territory, now that the interior and last line of fortresses was so nearly broken through. In pursuance of this design, Villars had, with the aid of all the most experienced engineers in France, and at a vast expense of labour and money, constructed during the winter a series of lines and field-works, exceeding any thing yet seen in modern Europe in magnitude and strength, and to which the still more famous lines of Torres Vedras have alone, in subsequent times, afforded a parallel. The works extended from Namur on the Meuse, by a sort of irregular line, to the coast of Picardy. Running first along the marshy line of the Canche, they rested on the forts of Montreuil, Hesdin, and Trevant; while the great fortresses of Ypres, Calais, Gravelines, and St Omer, lying in their front, and still in the hands of the French, rendered any attempt to approach them both difficult and hazardous. Along the whole of this immense line, extending over so great a variety of ground, for above forty miles, every effort had been made, by joining the resources of art to the defences of nature, to render the position impregnable. The lines were not continuous, as in many places the ground was so rugged, or the obstacles of rocks, precipices, and ravines were so formidable, that it was evidently impossible to overcome them. But whereever a passage was practicable, the approaches to it were protected in the most formidable manner. If a streamlet ran along the line, it was carefully dammed up, so as to be rendered impassible. Every morass was deepened, by stopping up its drains, or letting in the water of the larger rivers by artificial canals into it; redoubts were placed on the heights, so as to enfilade the plains between them; while in the open country, where no advantage of ground was to be met with, field-works were erected, armed with abundance of heavy cannon. To man these formidable lines, Villars had under his command one hundred and fifty-six battalions, and two hundred and twenty-seven squadrons in the field, containing seventy thousand infantry, and twenty thousand horse. He had ninety field guns and twelve howitzers. There was, besides, thirty-five battalions and eighty squadrons detached or in the forts; and, as Eugene soon took away twelve battalions and fifty squadrons from the Allied army, the forces on the opposite side, when they came to blows, were very nearly equal.[29]