The Percies had recently gained a victory for King Henry IV., whom they had so powerfully assisted in gaining his throne. They were about to turn their arms against him. Shakspeare attributes their discontent to the prohibition which the king put upon their setting ransoms upon their prisoners, a measure which deprived them of all the pecuniary advantage of the capture; but this interdiction had been frequent under the preceding reigns, particularly under Edward III., and King Henry IV. indemnified the Earl of Northumberland by granting vast domains to him. Another cause for anger had recently sprung up. During the lucky campaigns of Owen Glendwyr the latter had captured his old enemy, Lord Grey de Ruthyn, and Sir Edmund Mortimer, uncle of the young Earl of March, the legitimate heir to the throne. The relatives of Lord Grey had been authorized to redeem him; but the king had refused the same favor to the family of Sir Edmund. {368} Hotspur Percy had married his sister, and, acutely wounded by this refusal, he began to set on foot a conspiracy to overthrow the king and place the crown upon the head of the little Earl of March. He was confirmed in this resolution by the Archbishop of York, Scrope, brother of the favorite of Richard II.; and the conspirators did not hesitate to call Owen Glendwyr to their aid. He gave his daughter in marriage to Mortimer, and promised to invade England with twelve thousand Welshmen. The Earl of Douglas was liberated without any ransom, on condition of recrossing the frontier with a Scottish army. It is even said that Hotspur wrote to the Duke of Orleans, from whom King Henry had recently received a warlike challenge on account of the insults offered to Queen Isabel. So many movements had not escaped the vigilant eye of King Henry. Hotspur was marching forward, commanding the rebels in place of his father, who was ill; and supported by his uncle, the Earl of Worcester. Henry planted his army corps between the earls and Owen Glendwyr, with whom they were endeavoring to effect a junction. The Welshman had made no haste, and when, on arriving at Shrewsbury, Henry received the challenge of his enemies, it was conceived only in the name of the Percies. They reproached the king with his usurpation, the death of Richard, the captivity of the little Earl of March, his manœuvres in the election of Parliament, the levying of taxes which had not been voted by the Commons, &c. At the end appeared the real subject of the quarrel, the denial of the negotiations relating to Sir Edmund Mortimer. Henry IV. smiled bitterly and disdained to reply. "The sword shall decide," he said, "and I am assured that God will give me victory over perjured traitors." It was on the 20th of July, 1403; on the morrow the two armies found themselves face to face on Shrewsbury Plain. {369}