The Space Marines from the tabletop game, video game, and book series Warhammer 40K display many characters that medieval heroes tend to hold, especially in reference to those depicted in
The History of the Kings of Britain. Just as their medieval counter-parts fight to defend their people and secure land and resources for the citizens of their respective nations, the Space Marines are first and foremost the staunch protectors of the Imperium of Man, fighting bravely against foreign hordes and securing a place for the human race in the vast expanse of the Milky Way Galaxy. Just as Brutus was for the Trojans, or Arthur for the Britons, the Space Marines are renowned amongst the citizens of the Imperium as extremely formidable warriors, gifted with the blood of the Emperor's sons, they are more than man and are the finest soldiers the Imperium has to offer. Comparative to Christian heroes such as Arthur or of later medieval texts, the Space Marines are credited for their religious zeal for the one true faith, which is in this case, the Imperial Truth. Their religious fervor and reverence for the one true God is a detail that makes them more heroic, at least in accordance with medieval values. In addition, just as medieval heroes are to practice the code of chivalry, the Space Marines adhere to a chivalrous code of sorts, known as the Codex Astartes, which serves as a book of guidelines as to how warfare should be properly and honorably conducted. Similarly, in a world fraught with disloyalty and treachery, loyalty in highly valued amongst medieval characters as well as in 40K. Just as characters in medieval literature are prone to become turncoats for the sake of personal gain, Space Marines of weaker will power are prone to renouncing their faith in the Emperor and turning to serve the Ruinous Gods of Chaos. Thus, unwavering loyalty and unquestioning obedience for righteous authority are highly applauded features in both Space Marines and medieval heroes. In addition to being similar to the idealized attributes of medieval heroes, Space Marines also bear semblance to the more brutal and not-so-heroic attributes of those same heroes. Just as Brutus arrives on foreign shores and slaughters many on his journey to Isles of Britain, or Arthur waging war on the pagan Picts or Saxons, the Space Marines purge entire populations in the name of the Emperor and are revered as heroes for it. Whether it be civilian alien populations or human populations in revolt or in heresy against the Imperial Truth, the Space Marines have lead countless thousands of genocides throughout the millennia in order to maintain the tenuous peace that binds the Imperium together. However despite such atrocities the Space Marines are venerated as the exalted heroes of Mankind, just as medieval heroes who commit similar deeds are still held in heroic regards by the people whom they rule. All in all, the Space Marines of the Warhammer 40K universe, and the knights and heroes of medieval literature are all formidable warriors, ferociously loyal, religiously zealous, and willing to commit atrocities in the name of the greater good.
