at the battle of Najara (1367) Du Guesclin was again a prisoner in English hands, and Henry lost his throne.  Fever destroyed the victorious host, and the Black Prince, withdrawing into Gascony, carried with him the seeds of the disorder which shortened his days.  Du Guesclin soon got his liberty again; and Charles V., seeing how much his great rival of England was weakened, determined at last on open war.  He allied himself with Henry of Trastamare, listened to the grievances of the Aquitanians, summoned the Black Prince to appear and answer the complaints.  In 1369, Henry defeated Pedro, took him prisoner, and murdered him in a brawl; thus perished the hopes of the English party in the south.  About the same time Charles V. sent open defiance and declaration of war to England.  Without delay, he surprised the English in the north, recovering all Ponthieu at once; the national pride was aroused; Philip, Duke of Burgundy, who had, through the prudent help of Charles, lately won as a bride the heiress of Flanders, was stationed at Rouen, to cover the western approach to Paris, with strict orders not to fight; the Aquitanians were more than half French at heart.  The record of the war is as the smoke of a furnace.  We see the reek of burnt and plundered towns; there were no brilliant feats of arms; the Black Prince, gloomy and sick, abandoned the struggle, and returned to England to die; the new governor, the Earl of Pembroke, did not even succeed in landing:  he was attacked and defeated off Rochelle by Henry of Castile, his whole fleet, with all its treasure and stores, taken or sunk, and he himself was a prisoner in Henry’s hands.  Du Guesclin had already driven the English out of the west into Brittany; he now overran Poitou, which received him gladly; all the south seemed to be at his feet.  The attempt of Edward III. to relieve the little that remained to him in France failed utterly, and by 1372 Poitou was finally lost to England.  Charles set himself to reduce Brittany with considerable success; a diversion from Calais caused plentiful misery in the open country; but, as the French again refused to fight, it did nothing to restore the English cause.  By 1375 England held nothing in France except Calais, Cherbourg, Bayonne, and Bordeaux.  Edward III., utterly worn out with war, agreed to a truce, through intervention of the Pope; it was signed in 1375.  In 1377, on its expiring, Charles, who in two years had sedulously improved the state of France, renewed the war.  By sea and land the English were utterly overmatched, and by 1378 Charles was master of the situation on all hands.  Now, however, he pushed his advantages too far; and the cold skill which had overthrown the English, was used in vain against the Bretons, whose duchy he desired to absorb.  Languedoc and Flanders also revolted against him.  France was heavily burdened with taxes, and the future was dark and threatening.  In the midst of these things, death overtook the coldly calculating monarch in September, 1380.