Criccieth Castle a distant relation of Llywelyn ap Gruffudd, began an uprising against English rule that spread quickly through Wales. Several English-held towns were razed and Criccieth (along with Harlech Castle and Aberystwyth Castle) were besieged that winter. Its residents survived until spring when the castle was resupplied. In the 14th century the castle had a notable Welsh constable called Hywel ap Gruffydd, known as Howell the Axe, who fought for Edward III at the Battle of Poitiers in 1356. The castle was used as a prison until 1404 when Welsh forces captured the castle during the rebellion of Owain Glyndŵr. The
Monmouth Castle turmoil and conflict in Wales during the ten years of the Owain Glyndŵr rebellion did not directly affect Monmouth Castle as it was a stronghold of the region and lesser targets presented themselves more readily to essentially a guerilla army. However other local towns, settlements and castles were directly attacked with Grosmont and Abergavenny being razed and Crickhowell Castle and Newport Castle successfully attacked. Over the centuries, as its defensive function diminished, the outer bailey of the castle became increasingly used as a market place, later (and now) known as Agincourt Square. During the sixteenth century, when Monmouth became the