Henry's first care was to secure his ill-defined and ill-defended frontier, and to recover those border fortresses which had been wrested from Geoffrey by his enemies. In Normandy the Vexin, which was the true military frontier between him and France, and commanded the road to Paris, had been lost. In Anjou he had to win back the castles which had fallen to the House of Blois. His brother Geoffrey, Earl of Nantes, was dead, and he must secure his own succession to the earldom. Two rival claimants were disputing the lordship of Britanny, but Britanny must at all costs be brought into obedience to Henry. There were hostile forces in Angoumois, La Marche, Saintonge, and the Limousin, which had to be finally destroyed. And besides all this, it was necessary to enforce Eleanor's rights over Berri, and her disputed claims to supremacy over Toulouse and Auvergne. Every one of these projects was at once taken in hand. Henry's chancellor, Thomas Becket, was sent from England in 1158 at the head of a splendid embassy to the French court, and when Henry landed in France the success of this mission was declared. A marriage was arranged between his little son Henry, now three years old, and Louis' daughter Margaret, aged six months; and the Vexin was to be restored to Normandy as Margaret's dowry. The English king obtained from Louis the right to judge as lord of Anjou and seneschal of France between the claimants to Britanny; his first entry into that province was with full authority as the officer of France, and the whole army of Normandy was summoned to Avranches to enforce his judgment. Conan was made Duke of Britanny under Henry's lordship, and Nantes was given up into his hands. He secured by treaty with the House of Blois the fortresses which had fallen into their hands, and before the year was out he thus saw his inheritance in Anjou and Normandy, as he had before seen his inheritance in England, completely restored. In November he conducted the King of France on a magnificent progress through Normandy and Britanny, not now as a vassal requiring his help, but with all the pomp of an equal king.
Meanwhile Henry had been preparing an army to assert his sovereignty over Toulouse - a sovereignty which would have carried his dominions to the Mediterranean and the Rhone. The Count of St. Gilles, to whom it had been pledged by a former Duke of Aquitaine, and who had eighteen years before refused to surrender it on Eleanor's first marriage, now resisted the claims of her second husband also, and he was joined by Louis, who under the altered circumstances took a different view of the legal rights of Eleanor's husband to suzerainty. To France, indeed, the question was a matter of life and death. The success of Henry would have left her hemmed in on three sides by the Angevin dominions, cut off from the Mediterranean as from the Channel, with the lower Rhone in the hands of the powerful rival that already held the Seine, the Loire, and the Garonne. When, therefore, Henry's forces occupied the passes of the province, and in September 1159 closed round Toulouse itself, Louis threw himself into the city. Henry, profoundly influenced by the feudal code of honour of his day, inheriting the traditional loyalty of his house to the French monarchy, too sagacious lightly to incur war with France, too politic to weaken in the eyes of his own vassals the authority of feudal law, and possibly mindful of the succession to the French throne which might yet pass through Margaret to his son Henry, refused to carry on war against the person of his suzerain. He broke up the siege in spite of the urgent advice of his chancellor Thomas; and for nearly forty years the quarrel lingered on with the French monarchy, till the question was settled in 1196 by the marriage of Henry's daughter Joanna to Count Raymond VI. Thomas, who had proved himself a mighty warrior, was left in charge of the newly-conquered Cahors, while Henry returned to Normandy, and concluded in May a temporary peace with Louis. His enemies, however, were drawn together by a common fear, and France became the battle-ground of the rival ambitions of the Houses of Blois and Anjou. Louis allied himself with the three brothers of the House of Blois - the Counts of Champagne, of Sancerre, and of Blois - by a marriage with their sister only a month after the death of his own queen in September; and a joint attack was planned upon Henry. His answer was rapid and decisive. Margaret was in his keeping, and he at once married her to his son, took the Vexin into his own hands and fortified it with castles. His position in fact was so strong that the forced his enemies to a truce in June 1161.