The great rebellion began with a personal quarrel between Owen and his arrogant neighbour Lord Grey of Ruthin. In 1400 the king had summoned Owen to assist him in his Scottish expedition. The summons had been entrusted to Lord Grey to deliver; but he, wishing to sow discord between Henry and Owen, neglected to transmit it. The king was angry with Owen, and with greater justice Owen was angry with Grey. Owen's wrath took the eloquent form of a merciless raid upon his enemy's estates, in the course of {114} which certain members of his household were slain. Grey, determined to retaliate, gathered together his forces and marched against Glyndyfrdwy. But the whole country was now up in arms; and supported by a strong body of followers, Owen was able to burn the town of Ruthin to the ground. Owen then openly declared himself the deliverer of Wales from the English yoke; and so serious a view did the king take of the situation that, without delay, he marched into Carnarvonshire. He was greatly incensed; and his anger was proved by the burning, without any provocation, of the house of the Franciscans at Llan Vaes. Owen, not strong enough as yet to meet the king in battle, retired into the mountain recesses, and Henry had to content himself with declaring all his lands forfeited. Meanwhile the flame of rebellion spread; and Owen was joined not only by people from every part of Wales, but by young Welshmen from Oxford, from London, and from beyond the seas. He had now planted his standard of the red dragon on the slopes of Plinlimmon; and there, safe from the clutches of all invading armies, he proceeded with the task of organization, making frequent dashes into the neighbouring counties, and capturing towns, castles, {115} and abbeys. The capture of the strong castle of Conway by nephews of Owen in the spring of 1401 brought Henry again to Wales, this time accompanied by Earl Percy. Conway was quickly recaptured. Percy, after marching through Carnarvonshire, reached the foot of Cader Idris, where he won a victory. Nevertheless the crushing of the rebellion, and the capture of Owen, seemed to be as remote as ever. In the autumn of the same year the energetic and persistent king came again, marched through Merionethshire, harried Cardiganshire, and stabled his horses near the high altar of the abbey of Strata Florida. Owen meanwhile hung on the skirts of his army, capturing stragglers, and cutting off supplies; and again the baffled monarch was compelled to return to his own country.