The byzantine empire was scared that the Seljuks would push towards Constantinople. Pope Urban IIwants to take back the holy land and boost his own power.
The Christians laid siege on the city of Antioch and captured the city evan after they had to defend the city from backup Muslim soldiers. In 1099 The Crusader Kingdoms take jerusalem.
The HRE's army was defeated in Anatolia. A second army was focused on Damascus which was soundly defeated taking the french out of the crusades.
Spainish Christians beat the Muslims
Salah al-Din united the biggest Muslim empire since the Seljuks. He took back most of Palestine and Jerusalem. In 1191 Richard I forced the surrender if Arce. He then pushed on to Jerusalem but was not strong enough to take it .
In 1212 young peasants from France and Germany marched which barely even got to the holy land many sold into slavery
The Reconquista was when Queen Isabella and King Ferdinand worked to unite Spain as a Catholic country. They used the Inquisition to who were against the Muslims. They succeeded in their efforts and took the country from the Muslims in 1492