Mysticus, did the same. In such a predicament, Simeon demanded Pope John X (914-928) to send him an imperial crown and to recognize the head of the Bulgarian church as Patriarch. Naturally, Simeon had to promise to recognize the papal primacy in the Church. John X accepted Simeon's request and sent a solemn mission to Bulgaria, headed by Cardinal Madalbertus and John, illustrious Duke of Cumae. The papal mission reached Bulgaria at the end of summer or during the fall of 926, carrying a crown and scepter with which they would crown Simeon as Bulgarian Emperor. When the papal mission arrived in Preslav, Madalbertus started long negotiations with Simeon and the representatives of the Bulgarian church. Probably, Madalbertus convoked a church synod in Bulgaria as he later did in Split, in Croatia, on his way back to Rome in 928. The negotiations regarding ecclesiastical matters were successful, and Archbishop Leontius was created Patriarch in Preslav, still during Simeon's reign. Reasons for the war In 924 Simeon sent a large army against Zaharija in the Principality of Serbia. The Bulgarian armies ravaged Serbia and forced Zaharija to flee to Croatia. Serbia was annexed by Bulgaria by which Simeon considerably expanded his state. After Simeon's annexation of Serbia the Bulgarian state bordered the Croatian kingdom under Tomislav, who was a Byzantine ally. Croatia was now located between Bulgaria and the weakly defended Byzantine Theme of Dalmatia, a possible new target of Simeon. Tomislav received and protected the Serbs who were expelled by Simeon from Rascia. Tomislav may have been granted by the Emperor Romanos I Lekapenos some years previously with some form of control over the coastal cities of the Byzantine Theme of Dalmatia and rewarded with some share of the tribute collected from the cities, thus securing the friendship of Tomislav. These events were a sufficient proof to Simeon that the Croats took the side of the Byzantine Emperor and that they would support him actively in the future. Therefore, Simeon saw Croatia, harboring his enemies and allied to the empire, as a threat and he could not direct all his forces towards Byzamtium since there was nothing to prevent Croatia from striking his rear. The battle In 926 Simeon sent a large army to invade Croatia. The strength of Simeon's army is unknown. The commander of the Bulgarian forces in this battle was Duke Alogobotur. According to Byzantine historian Constantine