First Crusade

What happened

Pope Urban II called the First Crusade (1096) ostensibly to reclaim Jerusalem from Muslim Seljuk Turks. Tens of thousands of European knights, clergy, and peasants marched east. Crusaders massacred Jewish communities in the Rhineland en route. Armies fragmented en route; supply lines collapsed. Survivors reached Jerusalem (1099) and slaughtered 40,000-70,000 defenders and civilians—Muslim, Jewish, and Greek Christian alike. Crusaders established four kingdoms (Jerusalem, Antioch, Edessa, Tripoli). Most crusader states fell within a century; Jerusalem was retaken by Saladin (1187).

Why it mattered

The Crusades inaugurated a centuries-long cycle of religious warfare between Christendom and Islam that reshaped the Mediterranean and Levant. They catalyzed technological transfer (Greek mathematics, astronomy) that fed Renaissance Europe. The Crusader mythology persists in modern rhetoric (Eisenhower, Bush, Bin Laden) invoking crusades metaphorically. The Crusades represent colonialism's religious predecessor and remind us that 'holy war' rhetoric motivated imperial expansion and massacre.