I bet you didn’t know there was a Welsh Rising of 1256 did you? This date, even more than the Battle of Bryn Derwin in 1255, is the point at which Llywelyn ap Gruffydd began to assert his authority in Wales beyond Gwynedd and to place himself squarely in the forefront as the inheritor of his grandfather’s vision of a Wales united under one, supreme Prince.
In 1256, Prince Edward of England was only seventeen years old. He had been ceded lands in Perfeddwlad, or Gwynedd Is Conwy (Gwynedd east of the River Conwy), by his father, King Henry. But both his parents still held authority over them, for the most part, and had been responsible for overseeing their welfare. They had not done a good job, as usual giving sycophants and hangers-on Welsh lands about which none of the parties involved cared a whit.
These lands, by no coincidence, had been fully in the control of Llywelyn Fawr before his death, and at the death of Prince Dafydd, had fallen under English control. In November 1256, at the request of the people themselves, Llywelyn took his men across the Conwy River and into what was then English territory. They conquered the entire area, with the consent of the people in it, within a week.
Much of these lands Llywelyn then gave to Dafydd, his brother, whom he’d just released from prison. Only eighteen himself, Dafydd had united with Owain in 1255, but with his defeat, had suffered only a short incarceration before Llywelyn forgave him–and established him as a fully authoritative Prince of Wales in his own right.
As the Chronicle of the Princes states for 1256:
“In this year the gentlefolk of Wales, despoiled of their liberty and their rights, came to Llywelyn ap Gruffudd and revealed to him with tears their grievous bondage to the English; and they made known to him that they preferred to be slain in war for their liberty than to suffer themselves to be unrighteously trampled by foreigners. And Llywelyn at their instigation and by their counsel and at their request, made for Perfeddwlad, and with him Maredudd ap Rhys Gryg; and he gained possession of it all. And after that he took the cantref of Meirionydd into his hands. And the land that belonged to Edward, the earl of Chester, the son of king Henry, he gave to Maredudd ab Owain, and Builth he gave to Maredudd ap Rhys, and keeping naught for himself, but only fame and honor.”
Sources: Llywelyn ap Gruffydd by J. Beverly Smith