The crusades were a series of holy wars called by popes with the promise of indulgences for those who fought in them and directed against external and internal enemies of Christendom for the recovery of Christian property or in defense of the Church or Christian people. Crusades were characterized by the taking of vows and the granting of indulgences to those who participated. Like going on pilgrimage, to which they were often likened, crusading was an act of Christian love and piety that compensated for and paid the penalties earned by sin. It marked a break in earlier Christian medieval conceptions of warfare in that crusades were penitential warfare. Crusades combined the ideas of: a) Holy War and b) and Pilgrimage to produce the concept of indulgence.
The First Crusade (1096–1099)Four European nobles led the First Crusade. Close to 30,000 Crusaders fought their way through Anatolia, and headed south toward Palestine. In June of 1098, the Crusaders laid siege to the city of Antioch in Syria. Antioch was protected by a ring of walls. After nine months, the Crusaders found a way over the walls. Antioch fell to the Christians.
The Second Crusade (1146–1148) The Crusaders owed their early victories, in part, to a lack of unity among Muslim groups. When the Crusades began, the Seljuk empire was already crumbling into a number of smaller states. Muslims had trouble joining together to fight the invaders. When Muslims started to band together, they were able to fight back more effectively. In 1144, they captured Edessa, the capital of the northernmost crusader kingdom. Christians answered by mounting the Second Crusade.
The Third Crusade (1189–1192) Over the next few decades, Muslims in the Middle East increasingly came under common leadership. By the 1180s, the great sultan Salah al-Din called Saladin by Europeans, had formed the largest Muslim empire since the Seljuks. Salah al-Din united Egypt, Syria, and other lands to the east. He led a renewed fight against the Crusaders in the Holy Land. Salah al-Din quickly took back most of Palestine. In 1187, his armies captured Jerusalem.
Later Crusades The Crusades continued for another 100 years. Some Crusades were popular movements of poor people, rather than organized military campaigns. In 1212, for example, thousands of peasant children from France and Germany marched in a Children’s Crusade. Few, if any, ever reached the Holy Land. Some made it to European port cities, only to be sold into slavery by merchants. Some returned home. Many disappeared without a trace. The Christians The Crusades changed society, as well. Monarchs grew more powerful, as nobles and knights left home to fight in the Middle East. The increasing power of monarchs weakened feudalism. Contact with Middle Eastern cultures had a major impact on Christians’ way of life. In the Holy Land, Christians learned about new foods and other goods. They dressed in clothing made of muslin, a cotton fabric from Persia. They developed a taste for melons, apricots, sesame seeds, and carob beans. They used spices, such as pepper. After Crusaders returned home with these goods, European merchants earned enormous profits by trading in them. The Muslims Muslims did gain exposure to some new weapons and military ideas during the Crusades.Like Europeans, they began to adopt standing, or permanent, armies. Muslim merchants, especially in Syria and Egypt, earned riches from trade with Europe. This money helped to fund building projects, such as new mosques and religious schools. The Crusades also brought political changes, as Muslims united to fight their common foe. The Ayyubid dynasty founded by Salah al-Din ruled Egypt and parts of Syria and Arabia until 1250. The Jews During the First Crusade, European Jews suffered a series of violent persecutions. As Crusaders crossed northern France and Germany, some of them murdered whole communities of Jews. They destroyed synagogues and holy books. They looted homes and businesses. Some Crusaders tortured Jews to make them accept Christianity.
i got all this information from TCI and http://www.usna.edu/Users/history.com