To profit by this victory, the Portuguese monarch commanded his barons to make an irruption into Castile, while he himself despatched to the duke of Lancaster a circumstantial account of this signal success. The latter now burned to assert his rights by other means than threats, or by the mere report of his preparations; he actually left England, with a small but choice armament (about fifteen hundred knights, and as many archers), accompanied by his wife, the lady Constanza, and his three daughters. In July, 1386, he appeared off the coast of Galicia, and ultimately landed at El Padron; thence he proceeded to Santiago, where he was solemnly proclaimed king of Castile and Leon. In an interview with the king of Portugal, on the confines of the two states, both entered into a treaty offensive and defensive; and, to cement it the more strongly, agreed that the king should marry Philippa, daughter of the duke. In the meantime, the Castilian was not idle: he had obtained succours from his constant ally the French king and encouragement from Clement VII, the rival of Urban. In the spring of 1387, the duke and the Portuguese king arrived at Benavente; but their progress was stayed by the plague, which daily made great ravages in their ranks. After the conquest of a few towns and fortresses, the allied army retired into Portugal. The duke himself was seriously indisposed in body, and consequently dispirited. Their retreat was hastened by intelligence of the troubles which raged in England, and which ended in the imprisonment, and eventually the death of the unfortunate Richard II. The Castilian king dreaded the resumption of hostilities at a more favourable period. He proposed to the Plantagenet the marriage of his eldest son, Henry, with Catherine, daughter of the duke, by the princess Constanza, and, consequently, granddaughter of Pedro the Cruel. To this overture the duke lent a favourable ear; towards the close of the year the conditions were definitively arranged at Bayonne. The principal were that, if Henry died before the consummation of the marriage, the princess should be given to the next son, Don Ferdinand; that Constanza, mother of the princess, should receive in fief five or six towns in Castile, besides a revenue of 40,000 francs per annum; that the duke should receive 600,000 in gold, by instalments, as an indemnification for the expenses of the war; that both Constanza and her husband should renounce all claim to the Castilian crown; and that hostages should be given him as a security for the due performance of the first three. Thus, if the personal ambition of the Plantagenet remained without gratification, he had at least the satisfaction of seeing one of his daughters queen of Portugal, and the other destined to the throne of Castile. Early in the following year, Catherine, who was in her fourteenth year, was betrothed to Henry, who was only in his ninth, and who on this occasion assumed the title of prince of the Asturias.