
If you successfully complete a Jihad or Crusade, you'll get some florins, extra experience for all units that helped with the Crusade, and the general that conquered the target will get the maximum Crusader or Holy Warrior trait (with its useful bonuses to piety, chivalry and bonus fighting Muslims or Catholics). However, any army on crusade or jihad cannot attack other Catholic or Muslim factions respectively, and if you do not make sufficient progress towards the crusade target your troops will start to desert your army. When you join a crusade or jihad, that army can move MUCH farther, will not pay any upkeep costs, and has the option to recruit some special cheap mercenaries. Regardless, you can join a Crusade or Jihad by taking a General and 7 other units ouside a city, then from the general's information scroll there will be a "Join Crusade/Jihad" option.
