The decisive point in the campaign against Normandy was the capture of Château Gaillard, the key to the Seine valley, in May, 1204, after a siege of six months which seems to have justified its designer, save for a stone bridge which sheltered the engineers who undermined the outer wall. Western Normandy fell before an attack from the side of Brittany; the great fortresses of the centre, Argentan, Falaise, and Caen, opened their gates to Philip; and with the surrender of Rouen, 24 June, 1204, Philip was master of Normandy. John had lingered in England, doing nothing to support the defense, and when he crossed at last in 1206 he was obliged to sign a final surrender of all the territories north of the Loire, retaining only southern Poitou and Gascony. Gascony and England were united for two centuries longer, but the only connection was by sea. The control of the Seine and the Loire had been lost, and with that passed away the Plantagenet empire. * * * * * The results of the separation of Normandy from England have been a favorite subject with historians, and especially with those who approach the Middle Ages from the point of view of modern politics and modern ideas of nationality. It all seems so natural that Normandy should belong with France and not with England. Nationality, however, is an elusive thing, and many forces besides geography have made the modern map. England in the Middle Ages had much more in common with Normandy than she had with Wales or Scotland, while in feeling, as well as in space, the Irish Sea was wider than the Channel. From the English point of view there was nothing inevitable in the loss of Normandy. On the French side the matter is more obvious. If Paris was to be the capital, it must control the Seine and the Loire, and when it gained control of them, its position in France was assured. The possession of Normandy meant far more to France than to England. Moreover the conquest of Normandy cut England and France loose from each other. The Anglo-Norman barons must decide whether they would serve the king of England or the king of France, and they were quickly absorbed into the country with which they threw in their lot. It was no longer possible to play one set of interests against another; turned back on themselves, the English barons met John on their own ground and won the Great Charter, so that the loss of Normandy has a direct bearing on the growth of English liberty. “When the Normans became French,” concludes Powicke, “they did a great deal more than bring their national epic to a close. They permitted the English once more to become a nation, and they established the French state for all time.”[46]