Zeno since 484. Switching allegiances, Zeno subsequently sought to destroy Odoacer and then promised Theodoric the Great and his Ostrogoths the Italian peninsula if they were to defeat and remove Odoacer. As both Herwig Wolfram and Peter Heather point out, Theodoric had his own reasons to agree to this offer: "Theodoric had enough experience to know (or at least suspect) that Zeno would not, in the long term, tolerate his independent power. When Theodoric rebelled in 485, we are told, he had in mind Zeno's treatment of Armatus. Armatus defected from Basilicus to Zeno in 476, and was made senior imperial general for life. Within a year, Zeno had him assassinated." In 489, Theodoric led the Ostrogoths across the Julian Alps and into Italy. On 28 August, Odoacer met him at the Isonzo, only to be defeated. He withdrew to Verona, reaching its outskirts on 27 September, where he immediately set up a fortified camp. Theodoric followed him and three days later defeated him again. While Odoacer took refuge in Ravenna, Theodoric continued across Italy to Mediolanum, where the majority of Odoacer's army, including his chief general Tufa, surrendered to the Ostrogothic king. Theodoric had no reason to doubt Tufa's loyalty and dispatched his new general to Ravenna with a band of elite soldiers. Herwig Wolfram observes, "[b]ut Tufa changed sides, the Gothic elite force entrusted to his command was destroyed, and Theodoric suffered his first serious defeat on Italian soil." Theodoric recoiled by seeking safety in Ticinum. Odoacer emerged from Ravenna and started to besiege his rival. While both were fully engaged, the Burgundians seized the opportunity to plunder and devastated Liguria. Many Romans were taken into captivity, and did not regain their freedom until Theodoric ransomed them three years later. The following summer, the Visigothic king Alaric II demonstrated what Wolfram calls "one of the rare displays of Gothic solidarity" and sent military aid to help his kinsman, forcing Odoacer to raise his siege. Theodoric emerged from Ticinum, and on 11 August 490, the armies of the two kings clashed on the Adda River. Odoacer again was defeated and forced back into Ravenna, where Theodoric besieged him. Ravenna proved to be invulnerable, surrounded by marshes and estuaries and easily supplied by small boats from its hinterlands, as Procopius later pointed out in his History. Further, Tufa remained at large in the strategic valley of the Adige near Trent,