Crusader Capture of Jerusalem
After a siege of just over a month the First Crusade took Jerusalem and massacred much of its Muslim and Jewish population.

Émile Signol · Public domain · Source
Having taken Antioch (1098), the crusaders reached Jerusalem in June 1099, shortly after the Fatimids had recovered the city from the Seljuks. They crossed the walls with siege towers on 15 July and killed Muslims and Jews alike.
Godfrey of Bouillon was chosen ruler; after his death his brother Baldwin I took the title King of Jerusalem in 1100. The massacre was long remembered in the Islamic world.