The raid into the north began and was continued in a fashion not exactly leisurely, but methodically slow. It made at first through Périgueux to Brantôme. Thence up through the country of the watershed to Bellac. It turned off north-westward as far as Lussac, and thence broke back, but a little north of east, to Argenton. It will be evident from the trace of such a route that it had no definite strategic purpose. It was a mere raid: a harrying of the land with the object of relieving the pressure upon the north. It vaguely held, perhaps, a further object of impressing the towns of Aquitaine with the presence of a Plantagenet force. But this last feature we must not exaggerate. The Black Prince did not treat the towns he visited as territory ultimately to be governed by himself or his father. He treated them as objects for plunder. The pace and method with which all this early part of the business was conducted in the first three weeks of August may be judged by the fact that, measured along the roads the Black Prince followed, he covered between Bergerac and Argenton just on a hundred and eighty miles, and he did it in just under eighteen marching days. In other words, he kept to a fairly regular ten miles a day, and slowly rolled up an increasing loot without fatiguing his horses or his men. From Argenton, which he thus reached quite unweakened on the 21st of August, he made Châteauroux (rather more than eighteen miles off, but not nineteen by the great road) in two days, reaching it on the 23rd. Thence he turned still more to the eastward, and passed by Issoudun towards Bourges. This last excursion or "elbow" in the road was less strategically motiveless than most of the march; for the Prince had had news that some French force under the son of the French king was lying at Bourges, and to draw off such a force southward was part of the very vague plan which he was following. Unlike that string of open towns which the mounted band had sacked upon their way, Bourges was impregnable to them, for it was walled and properly defended. They turned back from it, therefore, down the River Yevre towards the Cher Valley again, and upon the 28th of August reached Vierzon, having marched in the five days from Châteauroux the regulation ten miles a day; for they covered fifty miles or a little more.