The Charlemagne scenario of Civilization IV simulates the competition for the title of Holy Roman Emperor in the Medieval era. There are five playable kingdoms (civs) in this game: Charlemagne (Austrasia), Gundobad (Burgundy), Chilperic I (Neustria), Eleanor (Aquitaine) and Alboin (Lombardy). (Note that any of these kings can be crowned Holy Roman Emperor, even though historically Charlemagne was the Holy Roman Emperor; hence the name of the scenario.) There are also six unplayable civilizations: the Romans (led by His Holiness), the Byzantines (led by Justinian I), the Arabs (led by Saladin), the Anglo-Saxons, the Bavarians, and the Saxons.
Gameplay is similar to the actual Civilization game, with two new concepts:
- Papal Favor. Simply put, Papal Favor determines how much the Pope likes you- at least, in the game. If you reach sufficient Papal Favor, you will be crowned Holy Roman Emperor, and if you maintain a high Papal Favor, you may receive the Papal Pikeman unit. The Papal Pikeman has 8 Strength, has a 35% bonus against melee units, and a 100% bonus against mounted units. Papal Pikemen spawn at your capital, and do not receive any experience points; XP must be earned.
- Supply Trains. Units in Charlemagne cannot get the Medic promotions, nor do they heal every turn. This is to simulate the actual manner of warfare in the medieval era. Instead, Supply Trains that start with the Medic I promotion must be built to heal units. Supply Trains have no attack and are a Classless Unit. It may be a good idea to stack a few Supply Trains with an invasion force.
Victory can be achieved in four ways: Domination victory, outright conquest of all your other rivals, time or being crowned Holy Roman Emperor.