The duke of Lancaster had in fact effected nothing: he had been obliged to retreat before the vastly superior armies brought to bear against him: but king John was still occupied in reducing the rebellious towns, when he heard somewhat tardily of the Black Prince's march. He instantly went to Chartres, and there gathered a large army, besides garrisoning every town on the Loire, to guard against the Black Prince crossing that river and making his way into Normandy. The prince had by this time reached Vierzon, after plundering and destroying unresisted across Angoumois, La Marche and Berri. He there heard that the king of France was assembling a large army on the Loire, and therefore gave up all thought of continuing his elaborate raid. One would have thought that the necessity of prompt action, seeing that he had only from 8000 to 10,000 men, would have been sufficiently obvious: but the chivalric point of honour was of so much importance that he wasted several days in taking the castle of Romorantin, which had offered unexpected resistance. It was a fortunate piece of rashness, for otherwise the French king would not have compelled him to fight at Poitiers. There seems to be no doubt that the Black Prince thought of crossing the Loire; but this gives no real support to the theory that his whole expedition was made in concert with Lancaster. Of course each was generally aware that the other was going to move, which would imply the possibility, if both succeeded, of their meeting somewhere thereabouts; but this is a very long way from deliberate co-operation. He might well have thought that if he could pass the Loire he would have as safe a refuge, would harass and perplex the French king more, and would not seem to have been driven to retreat; otherwise he would certainly have never gone near Poitiers, but would have followed a line of retreat as straight on Bordeaux as possible, every march in which would take him further from king John's overwhelming army. Some of the authorities trace his route, some do not; the places named do not always agree, and are not all to be certainly identified. The most precise of them says that he went straight to Tours, remained near that city several days hoping to cross the river there, and decamped south on hearing that the French king was crossing at Blois. The same account states that king John through his scouts was acquainted with the prince's movements: if so, one would think he ought to have made a little more haste. When he did move however the French king marched not straight towards his enemy, but in a direction intended to intercept his retreat, a piece of strategy which may seem obvious enough, but not so common in the middle ages. From Loches he directed his army on Poitiers, the main part with the king in person crossing the Vienne at the bridge of Chauvigny, fifteen miles east of that city. The slight information which each side had of the other, seems to have failed totally at the critical