Who was the secular leader in the Middle Ages known for promoting a strong, centralized government?

The correct answer is Charlemagne, as he was instrumental in the development of a strong, centralized government during the Middle Ages. As the King of the Franks and later the Emperor of the Romans, Charlemagne expanded his kingdom significantly and sought to unify Europe under his rule. He implemented administrative reforms that established a system of local governance through counts and appointed officials, which helped maintain control over his vast territory. This centralization was a key aspect of his reign, as he emphasized the importance of law and order, education, and cultural revival, which contributed to what is often referred to as the Carolingian Renaissance.

In contrast, while William the Conqueror did consolidate power after his conquest of England and laid the foundation for a centralized government, his influence was more localized compared to Charlemagne's. Richard the Lionheart is primarily associated with his role in the Crusades and spent much of his reign away from England, which affected his ability to govern. Henry II did promote legal reforms and centralized authority within England, but he operated in a different context and timeframe, coming after Charlemagne and not on the same scale in Europe. Thus, Charlemagne stands out as the primary figure in promoting a strong, centralized government during the Middle Ages.