It was, as we have seen, on the evening of Tuesday, September the 13th, that the Black Prince with his 7000 men and his heavy train of booty had marched into La Haye des Cartes, a small town upon the right bank of the Creuse, somewhat above the place where that river falls into the Vienne. His confidence that his well-mounted and light-armed troops could outmarch his pursuers was not yet shaken; he was even prepared to imagine that he had already shaken them off; but anyone who could have taken a general survey of all that countryside would have discovered how ill-founded was his belief. The great forces of the French king, coming down slantways from the north and east, had had nearly four miles to march to his three. Yet they were gaining on him. Edward had given the French king a day's advance by his hesitation before Tours, and the tardiness with which he had received news of John's crossing the Loire was another point in favour of the French. It was the Black Prince's business to get down on to the great road which has been the trunk road of Western France for two thousand years, and which leads from Paris through Châtellerault and Poitiers to Angoulême, and so to Bordeaux. If (as he hoped) he could advance so quickly as to get rid of the pursuit, so much the better. If he were still pressed he must continue his rapid marching, but, at any rate, that was the road he must take. To the simple plan, however, of reaching Châtellerault and then merely following the great road on through Poitiers, he must make a local exception, for Poitiers itself contained a large population, with plenty of trained men, munitions, and arms; and it was further, from its position as well as from its walls, altogether too strong a place for him to think of taking it. The town had been from immemorial time a fortress: first tribal (and the rallying point of the Gaulish Picts under the name of Limon); later, Roman and Frankish. The traveller notes to-day its singular strength, standing on the flat top and sides of its precipitous peninsula, isolated from its plateau on every side save where a narrow neck joins it to the higher land; it is impregnable to mere assault, half surrounded by the Clain to the east, and on the west protected by a deep and formidable ravine. It was absolutely necessary for the Prince not only to avoid Poitiers, but not to pass so close to it as to give the alarm. What he proposed to do, therefore, was to strike the great Bordeaux road at a point well south of the city, called Les Roches, and to do this he must engage himself within the broadening triangle which lies between the Clain and the Vienne: these rivers join their waters just above Châtellerault itself.