 The purpose of building the iron ring of castles was to control the native population of North Wales, particularly Gwynedd, which had been the main locus of resistance to the English crown for centuries .The jewel in the crown of the Iron Ring was Caernarfon Castle, which Edward intended to be his seat in Gwynedd and where he arranged for his son Edward II to be born.Many of the castles begun after the end of the war in 1282 were the work of master architect James of Saint George.