Meanwhile Edward had to face the constant hostility of the emperor.  Wenceslaus of Luxemburg, brother of Charles IV., had married the daughter and heiress of John III of Brabant, with the result of solidly establishing the house of Luxemburg in the strongest of the duchies of the Low Countries.  With the Luxemburger as with the Bavarian, Edward’s relations were unfriendly.  Two only of the Low German lords, the dukes of Gelderland and Juelich, were willing to take his pay.  Early in the war they were assailed by the Luxemburgers, and the contest occupied all their energies.  Thus Edward re-entered the struggle against France with no help save that of his own subjects.  Urban V. died at Avignon in 1370, and his successor, Gregory XI., was as little friendly to English claims in France as his predecessors had been.  Pope, emperor, and the Netherlandish princes, were all either French or neutral.  And in 1369 Peter of Castile lost his throne, and soon afterwards perished at his brother’s hands.  Henry of Trastamara, henceforth King of Castile, became the firm ally of the French, who had already the support of Aragon.  Even Charles the Bad thought it prudent to declare for France.

At each stage of the war the French took the initiative.  The appeal of the southern nobles was the beginning of a national movement which, before March, 1369, was supported by more than 900 towns, castles, and fortified places in Edward’s allegiance.  In April the French invaded Ponthieu and were welcomed as deliverers at Abbeville and the other towns of the county.  John of Gaunt led an army during the summer from Calais southwards.  He marched through Ponthieu, crossed the Somme at Blanchetaque, and ravaged the country up to the Seine.  Then he retired exhausted, having gained no real advantage by this mere foray.  Charles announced that, as Edward had supported the free companies, he fell under the excommunication threatened by the pope against the abettors of these pests of society, and that the vassals of the English crown were therefore relieved from allegiance to him.  Soon afterwards he declared that Edward had forfeited all his possessions in France.

Quercy and Rouergue, which had submitted last, were the first districts of Aquitaine to revolt.  Cahors declared for France as soon as the Black Prince was cited to Paris.  By the end of 1369 all Quercy had acknowledged Charles V., and John of Armagnac ruled Rouergue as his vassal.  It was the same in the Garonne valley, where towns which had no quarrel with English rule, were swept away by the strong tide of national feeling that surged round their walls.  A systematic attack was made upon the English power in Aquitaine.  Charles V. fitted out new armies in which the townsmen and the country-folk fought side by side with the nobility.  Two of his brothers, John, Duke of Berri, and Louis, Duke of Anjou, prepared to assail the intruders, Berri in the central uplands, Anjou in the Garonne valley.  It was not enough to recover what was lost.  Aggression must be met by aggression, and the Duke of Burgundy, Charles’ third brother, equipped a fleet in Norman ports, either to invade England or at least to cut off the Black Prince from his base.  Portsmouth was burnt, before England had made any effort to defend her shores.