Christianity is a religion that is very interactive with the religions of Islam and Judaism.
christianity to islam
These two religions share a common origin in the Middle East. Christians are known as "Children of the Book" by the Muslims. Muslim look at the belief of their Injil, original gospel of Jesus, important to the theories of the Islamic people. They view the current gospels as being corrupted. The Muslims are instructed to defend the Christian faith from aggressors in certain situations and under certain circumstances since treaties have been signed. The one who instructed this is Prophet Muhammad and under the document called "Achtiname of Muhammad". Both religions, at their core, share the "golden" commandments. But there are also many differences. Islam does not believe that Christianity is divided into the Holy Trinity. They believe that dividing Gods Oneness is a sin (Shirk).
Christianity to judaism
These two religions share historical roots in the Second Temple period but they split in the first centuries. Christians place great emphasis on the belief which focuses on the New Covenant and the Triune God which is made through Jesus himself. Judaism puts emphasis on the right of conduct and that is focused on Mosaic Covenant and that is the God of Israel is made with the Israelites. These beliefs are put into books. the Bible for Christians and the Torah and Talmud for the Israelites. Christians can obtain salvation from sinning through repentance of sin. Judaism believes in there people individually and collectively participating in eternal dialogues with the God of Tradition. Christians worship a Triune God that is human and Judaism emphasizes the Oneness of God and doesn't believe in a human form of God.
The crusades were a series of religious expeditionary wars blessed by Pope Urban II and the catholic church. Its goal was to restore Christian access to the holy places near Jerusalem. Jerusalem was a sacred city and the symbol of the three major Abrahamic faiths (Judaism, Christianity and Islam). The crusades was set when the Seljuk Turks decisively defeated the Byzantine army in the year 1071 and cut off the the Christian access to the city of Jerusalem. Alexis I, at the time emperor, feared that all of Asia minor would be overrun so he called on western leaders and the papacy to come to the aid of Constantinople. The undertaking of a pilgrimage that would free Jerusalem from the Muslim rule was his goal. Another cause was the destruction of many Christian sacred sites and the persecution of the Christians by the Fatimid caliph Al-Hakim. All the crusades compromised military units of Roman Catholics from all over western Europe, and were not under unified command. The main series of crusades, primarily against the Muslims in the levant, occurred between the years of 1095 and 1291. The later crusades failed and the crusaders were defeated and forced to return to their homeland. Several hundred thousand soldiers became crusaders by taking vows that the granted them plenary indulgence. The emblem of the crusaders is the Cross- crusades is derived from the french word that means "cross".