In an immediate sense, the Crusades had a terrible effect on some of
the Muslim and Jewish inhabitants of the Middle East. During the First
Crusade, for example, adherents of the two religions joined together to
defend the cities of Antioch (1097 CE) and Jerusalem (1099) from
European Crusaders who laid siege to them. In both cases, the Christians
sacked the cities and massacred the Muslim and Jewish defenders alike.