Five weeks of siege and 50,000 soldiers came down to a single breach. On July 15, 1099, Crusader knights scaled the walls of Jerusalem and poured into the holy city, ending a grinding campaign that had marched from Western Europe three years earlier. The assault, led by Godfrey of Bouillon and Raymond IV of Toulouse, shattered the Fatimid garrison within hours. What followed was a massacre: chronicles record the slaughter of Muslim and Jewish residents across the city's quarters, acts that shocked even contemporaries on both sides of the religious divide. The conquest fulfilled Pope Urban II's 1095 call to arms and planted a Latin Christian kingdom in the Levant that would survive, and antagonize, for nearly two centuries. The shock of July 15, 1099 galvanized the Islamic world, ultimately producing Saladin's reconquest of Jerusalem in 1187, and seeded centuries of crusading ideology whose echoes still surface in modern religious nationalism and Middle Eastern geopolitics today.