The Seljuk Turks take over Jerusalem thus, the Byzantine emperor asks for help from the Pope.
Let's sign a truce.
The Crusade goes to Jerusalem to capture the city from the Seljuk Turks. It'sa success because the Crusade took them by surprise.
The pope calls for a Crusade when the Muslims counter attack because the Christians don't treat them well. The Muslim leader Saladin takes Jerusalem back in 1187. This Crusade is a failure because the Muslims recaptured Jerusalem.
This Crusade was called the "Crusade of the Kings". In this Crusade the kings Saladin and Lionheart sign a truce, ending the third Crusade. This Crusade is a failure because the Muslims still control Jerusalem.
This Crusade was a complete and total failure. The Crusaders attacked Constantinople and for 3 days they smashed Christian icons, stole relics, and attacked women. The pope was extremely disappointed and the Byzantines never forgave Catholic Christians.
During all this the Western Europeans gained a bunch of new knowledge. Some of this included Architecture, as in domes and mosaics. They were able to make more accurate maps and more. Wealthy Europeans wanted Eastern goods like spices, sugar, silk, and lemons. The Crusades weakened Feudalism because Nobles freed their serfs when they sold their land when they joined the Crusades. Kings were also able to build stronger central government.