The Welsh had taken advantage of the king's difficulties to invade the adjoining counties, and "after their accustomed manner,"[9] carried off the cattle, and plundered and murdered the inhabitants, many of whom they also made prisoners. They laid siege to the castle of Montgomery, and took it by assault, slaying all the garrison. William in 1095 marched hastily into Wales, but found it impossible to reach the marauders, who kept to the cover of the woods and marshes, and among the mountains, watching their opportunity to slay any of the English and Norman troops whom they could reach unawares. Rufus pursued them over the hills; but his march was attended with heavy loss to his army, and he was at length compelled to retreat, "not without some note of dishonour." Two other expeditions met with no better success. Thereupon he left the conquest of Wales to his nobles, whose eagerness was whetted by grants of land in the unconquered districts. An army was despatched under the command of the Earl of Shrewsbury, and the Earl of Chester, who re-took the isle of Anglesea, of which the Welsh had obtained possession.[10] The inhabitants were maltreated or put to the sword; but, having received some reinforcements, a battle ensued, in which the Earl of Shrewsbury was slain. The victory, however, was on the side of the Earl of Chester, who remained for some time in Wales, desolating the country. While the Welsh were still unsubdued, Rufus received information of a powerful confederacy which had been formed against him in the north of England. The king had reason to suspect some of his nobles of disaffection, and especially Robert Mowbray, Earl of Northumberland, a powerful noble, whose long absence from court had excited suspicion. A royal proclamation was issued, calling upon every baron in the kingdom to appear at court at the approaching festival of Whitsuntide, on pain of outlawry. The Earl of Northumberland neglected to obey the summons, and the king immediately marched an army to Newcastle, where he surprised some of the earl's accomplices. He next besieged and took the castle of Tynemouth, and thence proceeded to Bamborough, an impregnable fortress, to which the Earl had retreated with his family. After various unsuccessful attempts to take this castle by storm, Rufus, who seems to have inherited much of the military talent of his father, adopted another plan of attack. He built a wooden fort opposite Bamborough, calling it _Malvoisin_, or "bad neighbour"; and, having placed a garrison in it, he withdrew the rest of his army. His lieutenants were directed to use every opportunity of inflicting damage upon the adherents of Earl Mowbray, or of gaining possession of his person.