A military order is a confraternity of knights, originally established as Catholic religious societies during the medieval Crusades for protection of Christians in response to the aggression and persecution of the Islamic conquests (623–1050) in the Holy Land and the Iberian Peninsula, as well as by Baltic paganism in Eastern Europe. Most members, often referred to as knights, were laymen, not priests, but sometimes cooperated with the clergy, taking vows such as poverty, chastity, and obedience according to monastic religious vows.