Alexander was a Byzantine military officer, active in the reign of Maurice. He is styled a taxiarch (Greek: ταξίαρχος) in the accounts of Theophylact Simocatta. He is known for his part in campaigns against the South Slavs.
Alexander is styled a taxiarch (Greek: ταξίαρχος) in the accounts of Theophylact Simocatta. This might be an attempt to translate a Latin title. He is unlikely to have served as a magister militum, always mentioned serving under other commanders. He might have been a comes rei militaris or a dux. In either case, Alexander was stationed in Thrace.
He is first mentioned in 593, serving under Priscus. Alexander was at that time tasked with leading a scouting party. He and his men crossed the river Helibakion (Ialomiţa River) in search of a group of Slavic raiders. The raiders attempted to escape through the local marshes, disorienting the Byzantines. Alexander attempted to set fire to the woods covering the rebels. But the material was too wet to catch fire. At that point, one of the raiders defected to Alexander's side. He was a Gepid who had briefly joined the Slavs, but apparently was not committed to their cause. He led Alexander to the hideout of his former allies. They were easily captured.
Alexander returned to Priscus' camp with the captives and valuable information. The raiders were spies employed by Musokios. The latter had just been informed of the defeat of Ardagast and had yet to react to it. Priscus and the defector started working on a trap to capture Musokios and his forces. In said plan, Alexander was assigned to lead an advance force.