a defense system along the Lower Danube in the border with the Byzantine Empire. Although Stephen III successfully defended his throne against the Byzantine intervention, he was obliged to renounce Sirmium and Dalmatia in favor of Emperor Manuel following an unsuccessful campaign in 1165. In order to recover the provinces, a Hungarian army under the command of Denis stormed into Sirmium in the spring of 1166. Henry of Mügeln relates that Stephen III instructed Denis to recover Sirmium for Hungary; in contrast, historian Paul Stephenson considered that the Hungarian king – who, as he argued, had no reason to support the violation of the peace treaty with Manuel – was unable to prevent "the uprising by his disgruntled nobles". Denis and his troops routed the local Byzantine contingent led by generals Michael Gabras – governor of the province – and Michael Branas, each other's rivals, and occupied the whole province with the exception of Zimony (present-day Zemun, Serbia). Byzantine historian Niketas Choniates narrates that Denis laid siege to the fort, but the arriving Byzantine imperial troops successfully repelled the attack. In order to retaliation, Emperor Manuel sent armies against Hungary, which plundered Transylvania. The Byzantine campaign caused great devastation in the eastern territories of the Kingdom of Hungary, forcing Stephen III to seek reconciliation and Henry Jasomirgott, Duke of Austria mediated an armistice. Despite that, following Denis' successful campaign, another Hungarian military leader Ampud invaded Dalmatia in the autumn of 1166. Emperor Manuel dispatched an army to Sirmium with his nephew and megas doux Andronikos Kontostephanos as commander and sent his fleet to Zimony after Easter 1167. According to John Kinnamos, Denis gathered an army of 15,000 men from 37 counties (their ispáns were also present) with him as commander-in-chief, also recruiting no small number of allied forces as mercenaries, especially Germans [Austrians], as Niketas Choniates writes. Both Byzantine chroniclers emphasize Denis' overconfidence. According to Choniates, Denis was "a man of mettle who had often drubbed the enemy's ranks, and, boasting over their successes, they marched out in a show of arrogance" and when the imperial army crossed the river "Istros" (i.e. Lower Danube), he "boasted loudly that he would gather once more the bones of the Romans fallen in battle and raise a sepulchral mound to serve as a trophy, as he had done in the past". Kinnamos narrates that Denis was "filled with courage and very ironically ordered