On the 15th of May the Emperor joined the Duke of York at Tournai, and the Archduke Charles brought the Austrian army from Landrecies to St. Amand, eleven miles to south of it. The field, on which the decisive action was to be fought, was one that had drunk deep of human blood. It may be described as the parallelogram enclosed by a line drawn south-eastward from Courtrai to Tournai, thence south-westward to Pont-à-Marque, thence north-westward through Lille to Wervicq, and thence north-eastward back to Courtrai. To east it is bounded by the Scheldt, to north by the Lys; and through the midst of it, flowing first from south to north past Pont-à-Marque and Cysoing to Lannoy, and thence westward into the Deule and so to the Lys, runs the Marque, a stream impassable except by bridges, owing to soft bottom and swampy banks. The principal bridges were those of Pont-à-Marque on the great road to Paris, and Pont-à-Tressin on the road from Tournai to Lille; but there were others on by-roads at Louvil, Bouvines, Gruson, Tressin, L’Hempenpont, Pont-à-Breug and Marque, most of them fortified and strongly held by the French. Two smaller streams of the same character as the Marque, but running from west to east, form also important obstacles within this arena, namely, the Espierres brook, which has its source close to Roubaix and flows into the Scheldt at Espierres, and the Baisieux brook, which rising near Hertain joins the Scheldt at Pont-à-Chin. The ground is mostly level, with the exception of the undulating heights that rise from the Lys, the low ridge upon which stood the villages of Roubaix and Lannoy, and the group of hills about Tournai itself; but it was thickly studded with villages, linked together by chains of innumerable cottages and farm-houses, which were all of them enclosed by hedges. The fields were cut up by swampy brooks and by a ramification of wide drains, which, with other enclosures, practically forbade the movements of troops except by road. The roads, however, even then were many; and the principal highways were nearly broad enough to permit an advance in column of half-companies;[234] but all of them, as well as the waterways, were lined with trees, making it extremely difficult to see the movements of troops from a distance. Thus it was and is a country unfit for cavalry, and far better adapted in that day to the tactics of the French than of the Allied infantry.[235]