Battle of Hattin
At Hattin in Galilee Saladin destroyed the main army of the Kingdom of Jerusalem and captured King Guy of Lusignan.

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Saladin had taken Egypt (1169) and Syria, encircling the crusader states. In July 1187 King Guy marched across a waterless plateau to relieve Tiberias and was surrounded at the Horns of Hattin, his men suffering from heat and thirst.
Most of the kingdom’s knights were killed or captured and the relic of the True Cross was lost. With no field army left, Acre and other cities surrendered one after another.