In 894, the Byzantine emperor Leo VI, then at war with Simeon, the Bulgarian czar (893–927), called the Hungarians to his aid. The Magyars, led by Árpád, crossed the Danube and attacked Bulgaria. The Bulgarians, in turn, appealed to the Pechenegs, now masters of the steppe, who attacked the Hungarians in the rear. Toward 850 or 860, driven from Levedia by the Pechenegs, they entered Atelkuzu (Etelköz) taking refuge in the mountains of Transylvania. At that moment, Arnulf, duke of Carinthia, at war with the Slav ruler Svatopluk, prince of Great Moravia (885–894), decided like the Byzantines to appeal to the Hungarians. The Hungarians overcame Svatopluk, who disappeared in the conflict (895). The Magyars reached the Danube river basin around 880. As the vanguard and rearguard, the Kabars, or Cowari as they were known in Latin, assisted in the Magyar invasion of Pannonia and the subsequent formation of the Principality of Hungary in the late 9th century. Great Moravia collapsed, and the Hungarians took up permanent abode in Hungary (907).