Dom John then took upon himself the title of Defender of the Realm; but he knew how little chance Portugal could have against Castile without some powerful ally, and he therefore sent first Thomas Daniel and Lourenço Martins, and then his Chancellor and the Master of the Knights of Santiago to beg for help from England. The longed-for aid seemed tardy, and Dom John proceeded to put Lisbon in a state of defence, and despatched the “Holy Constable” to raise an army in the northern provinces. In 1384, John of Castile slowly entered Portugal with a great army and joined Donna Leonor at Santarem. But the allies soon quarrelled as to the government in future of the country they both believed to be already conquered, and Donna Leonor recommended her adherents to join Dom John. Not satisfied with this, she planned to poison her son-in-law; but her intention was discovered in time, and the wicked queen was sent by John of Castile to the convent of Tordesillas, in his dominions, where she ended her days in 1386. This act of justice done, the king of Castile laid siege to Lisbon. The resistance was worthy of the cause, which was indeed that of the continued existence of Portugal as an independent country. The priests fought at the head of their parishioners; the archbishop of Braga behaved as a gallant knight; and Dom John showed his fitness to be the monarch of a warlike people. A terrible pestilence, which broke out in the besiegers’ camp, did more mischief than the bravery of the besieged, and John of Castile had to retire discomfited. But it availed little to have repulsed one Spanish army; the relative sizes of Portugal and Castile, made it obvious that the struggle would be a severe one; the independence of Portugal was at stake, and the Portuguese fought as men fight for their existence as a nation. The heroic Constable enforced the lesson of the successful defence of Lisbon by his defeat of the Castilians at Atoleiros, but it was felt to be necessary to take yet stronger measures, if the war was to end in a triumph.