"We must recapture the holy lands! Death to other people!"
The European dudes set out to retake various lands. They began in 1095 after the earliest capture of Jerusalem by Seljuk Turks brought call from the pope to recover the holy lands of Palestine from the Muslims. They succeeded but then lost it again. They tried again and so on. King Richard I helped with the 3rd crusade (1189) and got captured on the way back.