During the People's Crusade, thousands of Jews were murdered in what is now called the Rhineland massacres.
The Islamic prophet Muhammad founded Islam in the Arabian Peninsula and had united much of Arabia into a single polity by his death in 632.
Arab power expanded rapidly in the 7th and 8th centuries largely by military conquest.
Volunteers became Crusaders by taking a public vow and receiving plenary indulgences from the Church.
Some were hoping for a mass ascension into heaven at Jerusalem or God's forgiveness for all their sins.
The Crusades were a series of religious wars sanctioned by the Latin Church in the medieval period.
The most commonly known Crusades were the campaigns in the Eastern Mediterranean aimed at recovering the Holy Land from Muslim rule, but the term "Crusades" is also applied to other church-sanctioned campaigns.The initial success of the Crusade established the first four Crusader states in the Eastern Mediterranean: the County of Edessa, the Principality of Antioch, the Kingdom of Jerusalem and the County of Tripoli.The enthusiastic response to Urban's preaching from all classes in Western Europe established a precedent for other Crusades.However, the Crusades had a profound impact on Western civilisation: they reopened the Mediterranean to commerce and travel (enabling Genoa and Venice to flourish); they consolidated the collective identity of the Latin Church under papal leadership; and they constituted a wellspring for accounts of heroism, chivalry, and piety that galvanised medieval romance, philosophy, and literature.The Crusades also reinforced the connection between Western Christendom, feudalism, and militarism.The Principality of Armenian Cilicia was a Crusader state under Armenian (Rubenid) rule.