1. 771 AD: Charlemagne becomes the King of the Franks.
2. 774 AD: Charlemagne conquers the Lombard Kingdom in Italy, expanding his territory.
3. 799 AD: Pope Leo III is attacked in Rome and seeks Charlemagne's assistance.
4. December 23, 800 AD: Charlemagne arrives in Rome and meets with Pope Leo III.
5. December 25, 800 AD: During a mass at St. Peter's Basilica, Pope Leo III crowns Charlemagne as Emperor of the Romans, also known as the Holy Roman Emperor.
6. 812 AD: Charlemagne issues the Constitutio Romana, a document outlining the relationship between the Pope and the Holy Roman Emperor.