Isaac attempted to forge a secret alliance with Saladin to impede Frederick's progress in exchange for his empire's safety. Fearful that Barbarossa intended to unseat him, Isaac ordered his army, under the "protostrator" Manuel Kamytzes, to accompany and harass the Crusaders by attacking their foraging parties. About 22 November 1185, with some 2,000 horsemen, Kamytzes moved to set up an ambush for the Germans' supply train near Philippopolis, where the German emperor was staying, around 22 November 1189. The Germans were informed of this from the Armenian inhabitants of the fortress of Prousenos, where Kamytzes had set up his main camp, and set out with 5,000 cavalry to attack the Byzantine camp. The two forces met by accident near Prousenos, and in the ensuing battle, Kamytzes' men were routed. The historian Niketas Choniates, who was an eyewitness, writes that the Byzantines fled as far as Ohrid, and that Kamytzes did not rejoin his men until three days after the battle.