Immediately after his election to the crown, Arthur found himself opposed by eleven kings and one duke, who with a vast army were actually encamped in the forest of Rockingham. By Merlin’s advice Arthur sent an embassy to Brittany, to solicit the aid of King Ban and King Bohort, two of the best knights in the world. They accepted the call, and with a powerful army crossed the sea, landing at Portsmouth, where they were received with great rejoicing. The rebel kings were still superior in numbers; but Merlin, by a powerful enchantment, caused all their tents to fall down at once, and in the confusion Arthur with his allies fell upon them and totally routed them.
After defeating the rebels, Arthur took the field against the Saxons. As they were too strong for him unaided, he sent an embassy to Armorica, beseeching the assistance of Hoel, who soon after brought over an army to his aid. The two kings joined their forces, and sought the enemy, whom they met, and both sides prepared for a decisive engagement. “Arthur himself,” as Geoffrey of Monmouth relates, “dressed in a breastplate worthy of so great a king, places on his head a golden helmet engraved with the semblance of a dragon. Over his shoulders he throws his shield called Priwen, on which a picture of the Holy Virgin constantly recalled her to his memory. Girt with Caliburn, a most excellent sword, and fabricated in the isle of Avalon, he graces his right hand with the lance named Ron. This was a long and broad spear, well contrived for slaughter.” After a severe conflict, Arthur, calling on the name of the Virgin, rushes into the midst of his enemies, and destroys multitudes of them with the formidable Caliburn, and puts the rest to flight. Hoel, being detained by sickness, took no part in this battle.
This is called the victory of Mount Badon, and, however disguised by fable, it is regarded by historians as a real event.