How did Geoffrey of Monmouth help establish the Arthurian legend in continental Europe?

Geoffrey of Monmouth played a pivotal role in establishing the Arthurian legend in continental Europe through his influential work, the Historia regum Britanniae (c. 1135–1138). Although his account was largely a fictionalized narrative rather than a historical record, it introduced the figure of King Arthur to a wide European audience, transforming him from a figure of local Welsh tradition into a celebrated, triumphant world conqueror.123

Geoffrey’s work provided the foundational framework for the "matter of Britain" (matière de Bretagne), which later medieval writers—particularly in France—expanded upon. By framing Arthur’s reign as a glorious era that paralleled the grandeur of figures like Charlemagne and Alexander the Great, Geoffrey created a compelling narrative that inspired subsequent authors, such as Wace and Chrétien de Troyes, to develop the complex knightly romances and themes that define the modern Arthurian legend. Additionally, his inclusion of the enchanter Merlin and his prophecies further cemented the popularity of this material across the continent.2314