Frederick I, Holy Roman Emperor responded to the call after setting his affairs of state in order and urging Philip Augustus to join as well.

[7] He took up the Cross at an imperial diet in Mainz Cathedral on 27 March 1188 and was the first to set out for the Holy Land in May 1189 with an army of 30,000–600,000 men, including 15,000–20,000 knights, according to contemporary accounts.

After passing through today's Hungary, Serbia, Bulgaria and the Byzantine Empire, the forces arrived in Anatolia, held by the Seljuk Sultanate of Rûm.

[14] Seljuk records attribute the Crusader victory to a devastating heavy cavalry charge which supposedly consisted of 7,000 lancers in white clothing and mounted on snow-white horses.

Barbarossa refused, supposedly saying "Rather than making a royal highway with gold and silver, with the help of our Lord Jesus Christ, whose knights we are, the road will have to be opened with iron".

[12][16] While some German commanders advised heading directly through Cilician Armenia to the Levant, Emperor Frederick insisted on taking Iconium to assure his army's food and horse shortage, so on 17 May the Crusaders camped in the "garden and pleasure ground of the sultan" outside the city, where they found plenty of water.

[1] The city fell easily; Duke Frederick was able to assault and take the walls with little resistance, and the garrison failed to put up much of a fight before surrendering altogether.

[22][23] There they bought over 6,000 horses and mules at steep prices, as well as an unknown number of donkeys, and stocked themselves with bread, meat, butter and cheese.

[27] The Turks lost 3,000 killed at the field battle on 18 May according to the History of the Expedition of the Emperor Frederick (Historia de Expeditione Friderici Imperatoris), a contemporary German chronicle relying on eyewitness accounts from the participating Crusaders and completed by an Austrian cleric called Ansbert no later than 1200.