Why did some historians call Charlemagne the greatest military leader of the middle ages?

Historians often regard Charlemagne as the greatest military leader of the Middle Ages due to his extensive conquests and the establishment of a vast empire that united much of Western Europe. His strategic military campaigns, particularly against the Saxons and the Lombards, expanded his realm and spread Christianity. Additionally, Charlemagne's ability to effectively organize and lead diverse troops, along with his innovative use of cavalry, showcased his military prowess. His legacy as a unifying figure laid the groundwork for the future of European politics and culture.