However, as a border town, its prosperity suffered after nearby areas, including Usk and Grosmont, were devastated through attacks by supporters of Owain Glyndŵr around 1405, though Monmouth itself did not come under attack.
Sayangnya, sebagai kota perbatasan, kemakmurannya dipengaruhi oleh daerah sekitarnya, termasuk Usk dan Grosmont, yang hancur akibat serangan para pendukung Owain Glyndŵr sekitar tahun 1405, meski Monmouth sendiri tidak diserang.