King Arthur (2004) on Netflix

This original portrayal of "Arthur", as opposed to the mystical elements of the tale in past Arthur films, uses names and other elements from the traditional, medieval, Catholic Arthurian cycle in a very different, yet historically less implausible, almost realistic plot. Around 400 AD, the Roman empire, stretched across many nations, from Arabia to Britain, collapsed and skirmishes over power broke out in outlying countries. The conquering Romans become impressed with the weaponry and fighting skills of the warrior Sarmatian people, which have to send their sons to serve Rome fifteen years in the cavalry before these knights may return home. Arthur is Artorius Castus, whose future Knights of the Round Table, eager to achieve their freedom, are charged by bishop Germanius with one final task before their discharge: a Roman estate tyrant and his family, especially adolescent son Alecto, who is selected for a great future in Rome, must be rescued thereto from the invading Saxons, whose ruthless warrior-king orders his conquering tribal army to pillage and burn entire villages down. But there is another danger lurking on the road to freedom - the Woads, Celtic Britton rebels who hate the Romans, lead by the 'magician' Merlin, who however realizes Rome is no longer the main threat and offers Artorius a novel alliance after sparing his life in an ambush.