Historical meaning of an army's name in Sengoku era 美濃八千騎


美濃八千騎

I read a historical novel with Sengoku era setting , and there's a character
mentioned about this name of an army. If you know about it's historical
meaning please explain.

Context is an enemy's captain yelling at his troops when they can't fight
against the protagonist.

Enemy Captain「ええい！何をやっておるのだ！たかが山賊に後れを取るなど、日の本最強である美濃八千騎の名の穢れであるぞ！」

