However, Gabinius abandoned his plans, opting to intervene in Ptolemaic Egyptian affairs instead.[6] Mithridates proceeded to invade Babylonia on his own with some initial success, but was soon confronted by the Parthian commander Surena's army.[7] Gabinius' successor Crassus also sought to ally himself with Mithridates and invaded Parthia's client state Osroene in 54 BC, but wasted most of his time waiting for reinforcements on the Balikh River's left bank, while Surena besieged, defeated and executed Mithridates in Seleucia on the Tigris. Orodes, now unopposed in his own realm, marched north to invade Rome's ally Armenia, whose king Artavasdes II soon defected to the Parthian side.[6]