Soon after the conclusion of the Byzantine–Norman wars in 1185, the Byzantine emperor Isaac II Angelos received word that a Third Crusade had been called due to Sultan Saladin's 1187 conquest of Jerusalem. Isaac learnt that Barbarossa, a known foe of his empire, was to lead a large contingent in the footprints of the First and Second crusades through the Byzantine Empire. Isaac II interpreted Barbarossa's march through his empire as a threat and considered it inconceivable that Barbarossa did not also intend to overthrow the Byzantine Empire. As a result of his fears, Isaac II imprisoned numerous Latin citizens in Constantinople. In his treaties and negotiations with Barbarossa (which exist preserved as written documents), Isaac II was insincere as he had secretly allied with Saladin to gain concessions in the Holy Land and had agreed to delay and destroy the German army.