Hungarian forces supported the Serbs during the emperor's campaign. The Hypatian Codex says that Géza referred to his war against Emperor Manuel when excusing himself for refusing to send reinforcements to Iziaslav II whom Yuri Dolgorukiy, Prince of Suzdal, expelled from Kiev in August 1149. Hungarian auxiliaries supported Iziaslav II to reoccupy Kiev in the early spring of 1150, but before long Yuri Dolgorukiy expelled Iziaslav from the town. In autumn, Géza led his army against Volodimirko of Halych, who was Yuri Dolgorukiy's close ally. He captured Sanok, but Volodimirko bribed the Hungarian commanders, who persuaded Géza to leave Halych before November. A "countless allied force of Hungarian cavalry as well as of the heterodox Chalisoi" had supported the Serbs in the same year, according to the contemporaneous John Kinnamos, but the Byzantine army routed their united troops on the river Tara in September. The Byzantine victory forced Uroš II of Serbia to acknowledge the emperor's suzerainty. Emperor Manuel launched a retaliatory campaign against Hungary and ravaged the lands between the rivers Sava and Danube. Assisted by Byzantine troops, the pretender Boris also broke into Hungary and devastated the valley of the river Temes. Géza, who had just returned from Halych, did not want to "involve the remaining Hungarian force in destruction" and sued for peace. The peace treaty was signed in late 1150 or early 1151. Géza met Henry Jasomirgott which contributed to the normalization of their strained relations in 1151. He sent reinforcements to Iziaslav II who again reoccupied Kiev before April 1151. Three months later, Volodimirko of Halych routed a Hungarian army that was marching towards Kiev. Frederick Barbarossa, the newly elected King of Germany, demanded the German princes' consent to wage war against Hungary at the Imperial Diet of June 1152, but the princes refused him "for certain obscure reasons", according to Otto of Freising. Géza invaded Halych in the summer of 1152. The united armies of Géza and Iziaslav defeated Volodimirko's troops at the San River, forcing Volodimirko to sign a peace treaty with Iziaslav. Pope Eugenius III sent his envoys to Hungary to strengthen the "faith and discipline" of the Hungarian church. Géza forbade the papal envoys to enter Hungary, which shows that his relationship with the Holy See had deteriorated. Géza planned to invade Paristrionthe Byzantine province along the Lower Danubein the spring of 1153. According to John Kinnamos, Géza sought vengeance for