When the Crusades ended in 1192, Richard I of England and Salah al-Din signed a treaty allowing Muslims to keep cities near Palestine and Christians access to Jerusalem. Further Crusades occurred in 1212 and an unsuccessful Children's Crusade was led by peasant children. Meanwhile, the Reconquista involved the battle for control of the Iberian Peninsula between Christians and Muslims, with Muslims gradually losing more land. In the 1400s, Queen Isabella and King Ferdinand unified Spain as Catholic through the Inquisition, harshly persecuting converted Muslims and Jews, burning thousands at the stake. After the Crusades, the Mongols also invaded Muslim lands led by Genghis Khan, defeating the Sel