Crusades are "Holy Wars" fought by Catholics against Muslims to take control of the holy land (Jerusalem, Acre, etc.). you can only participate in them if you are of the Catholic religion, not Orthodox. Only the Pope and Catholic factions can call crusades. You cannot participate in a crusade if you are excommunicated. Note however, if you are on a crusade and you get excommunicated your army might desert.
Entering a crusade gives the player access to special crusader units and sometimes a "fair in rule" trait. All crusader units have free upkeep until the crusade ends. These units remain after the crusade is finished, but they will then require upkeep. Joining a crusade may allow access to (depending on regional availability):
- Great Cross: A crusading standard somewhat like the Carroccio standard.
- Crusader Knights: Similar to French Noble Knights
- Crusader Sergeants: Crusading Armoured Sergeants
- Unhorsed Knights: Powerful Dismounted Knights
- Note: Knights Templar and Knights Hospitaller become available through their respective guilds, which become available after crusade activities.
Once in a while the Pope calls a crusade, and usually calls the first one against a far-off Islamic city. This automatically creates a mission in the player's mission log, but the Pope may also require a specific character to join the crusade as a separate mission. If nobody joins then the crusade ends, and unsuccessful crusades will eventually expire.
Crusades are called on rebel cities, cities of Islam, and excommunicated cities. You can call a crusade if your favour points are high enough. The pope will probably call a crusade on the first city it sees.
The Muslim equivalent is the Jihad.
The Crusades were a series of military campaigns during the time of Medieval England against the Muslims of the Middle East. In 1076, the Muslims had captured Jerusalem - the most holy of holy places for Christians. Jesus had been born in nearby Bethlehem and Jesus had spent most of his life in Jerusalem. He was crucified on Calvary Hill, also in Jerusalem. There was no more important place on Earth than Jerusalem for a true Christian which is why Christians called Jerusalem the "City of God".
However, Jerusalem was also extremely important for the Muslims as Muhammad, the founder of the Muslim faith, had been there and there was great joy in the Muslim world when Jerusalem was captured. A beautiful dome - called the Dome of the Rock - was built on the rock where Muhammad was said to have sat and prayed and it was so holy that no Muslim was allowed to tread on the rock or touch it when visiting the Dome.
Therefore the Christian fought to get Jerusalem back while the Muslims fought to keep Jerusalem. These wars were to last nearly 200 years
The First Crusade : 1096 to 1099
The Second Crusade : 1147 to 1149
The Third Crusade : 1189 to 1192
The Fourth Crusade : 1201 to 1204
The Fifth Crusade : 1218 to 1221
The Sixth Crusade : 1228 to 1229
The Seventh Crusade : 1248 to 1254
The Eighth Crusade : 1270
In 1212 what became known as the Children’s Crusade also occurred.