Lord Grey rode with his men to Ruthyn, and the forty men-at-arms from Ludlow returned to that town; where, a few days later, the news arrived that Glendower, with a large following, had established himself on the rugged height of Corwen, and was engaged in strengthening the ancient fortifications on its summit.
For a time there was quiet on the border, and then came the startling news that Glendower had suddenly surprised, plundered, and burnt to the ground the town of Ruthyn, where a fair was being held at the time.
Then, having obtained great booty, and greatly injured his enemy Lord Grey, he again retired.

It was evident that no local force of sufficient strength could be found to pursue Glendower into his fastnesses on the ranges of Berwyn and Snowdon, and nothing was done until, three months later, the king, on his return from Scotland, marched into Wales with the levies of Warwickshire, Leicestershire, and eight other adjacent counties, while orders were issued to the people of Shrewsbury, and other towns on the eastern border, to hold themselves in readiness to repel any movement of the Welsh in that direction.
The king, however, accomplished nothing.

Glendower, with his following, took refuge among the forests of Snowdon; and the English army marched along the north coast, putting to the sword a few bands of peasantry, who ventured to oppose them; crossed to the Isle of Anglesey and, entering the Franciscan monastery of Llanfaes, slew some of the monks and carried the rest to England, and established a community of English monks in the convent.

This was done because the Franciscans had been supporters of the late king, and were believed to have given aid and encouragement to Glendower.
The Welsh expedition was, therefore, no more successful than the Scotch had been.
For a time, matters settled down.

Glendower was occupied in strengthening his position.