The lords of Aquitaine shrank from fighting for such a cause, but in spite of their protests and the reluctance of the English council to embark in so distant a struggle Edward held that he had no choice save to replace his ally, for to leave Henry seated on the throne was to leave Aquitaine to be crushed between France and Castille. [Sidenote: Charles the Fifth] The after course of the war proved that in his anticipations of the fatal result of a combination of the two powers Edward was right, but his policy jarred not only against the universal craving for rest, but against the moral sense of the world. The Black Prince however proceeded to carry out his father's design in the teeth of the general opposition. His call to arms robbed Henry of the aid of those English Companies who had marched till now with the rest of the crusaders, but who returned at once to the standard of the Prince; the passes of Navarre were opened with gold, and in the beginning of 1367 the English army crossed the Pyrenees. Advancing to the Ebro the Prince offered battle at Navarete with an army already reduced by famine and disease in its terrible winter march, and Henry with double his numbers at once attacked him. But in spite of the obstinate courage of the Castilian troops the discipline and skill of the English soldiers once more turned the wavering day into a victory. Du Guesclin was taken, Henry fled across the Pyrenees, and Pedro was again seated on his throne. The pay however which he had promised was delayed; and the Prince, whose army had been thinned by disease to a fifth of its numbers and whose strength never recovered from the hardships of this campaign, fell back sick and beggared to Aquitaine. He had hardly returned when his work was undone. In 1368 Henry reentered Castille; its towns threw open their gates; a general rising chased Pedro from the throne, and a final battle in the spring of 1369 saw his utter overthrow. His murder by Henry's hand left the bastard undisputed master of Castille. Meanwhile the Black Prince, sick and disheartened, was hampered at Bordeaux by the expenses of the campaign which Pedro had left unpaid. To defray his debt he was driven in 1368 to lay a hearth-tax on Aquitaine, and the tax served as a pretext for an outbreak of the long-hoarded discontent. Charles was now ready for open action. He had won over the most powerful among the Gascon nobles, and their influence secured the rejection of the tax in a Parliament of the province which met at Bordeaux. The Prince, pressed by debt, persisted against the counsel of his wisest advisers in exacting it; and the lords of Aquitaine at once appealed to the king of France. Such an appeal was a breach of the treaty of Bretigny in which the French king had renounced his sovereignty over the south; but Charles had craftily delayed year after year the formal execution of the renunciations stipulated in the treaty, and he was still able to treat it as not binding on him.