Odaenathus assembled the Palmyrene army and Syrian peasants, then marched north to meet the Persian emperor, who was returning to Persia. The Palmyrene monarch fell upon the retreating Persian army between Samosata and Zeugma, west of the Euphrates, in late summer 260. He defeated the Persians, expelling Shapur I from the province of Syria. In early 261, Fulvius Macrianus headed to Europe accompanied by Macrianus Minor, leaving Quietus and Balista in Emesa. Odaenathus' whereabouts during this episode are not clear; he could have distributed the army in garrisons along the frontier or might have brought it back to his capital. The Palmyrene monarch seems to have waited until the situation clarified, declaring loyalty to neither Fulvius Macrianus nor Gallienus. In the spring of 261, Fulvius Macrianus arrived in the Balkans but was defeated and killed along with Macrianus Minor; Odaenathus, when it became clear that Gallienus would eventually win, sided with the Emperor and marched on Emesa, where Quietus and Balista were staying. The Emesans killed Quietus as Odaenathus approached the city, while Balista was captured and executed by the King in autumn 261.