Final answer:
Charlemagne was a pivotal figure in European history who ruled the Franks, expanded the empire through military campaigns, and supported church and cultural reforms.
Step-by-step explanation:
The person who was a political adviser, war leader, and ruled the Franks was Charlemagne. He was the son of Pépin and vastly expanded the Frankish empire during his reign from 768 to 814. Charlemagne is known for his numerous military campaigns across central Europe, reorganization of the government, efforts to revive learning, and for strengthening the Christian church. His reign saw the formation of the Holy Roman Empire, and he was crowned 'Emperor of the Romans' by Pope Leo III on Christmas Day in the year 800. However, the empire he built did not last beyond a few generations, giving way to the system of feudalism.