This article evaluates the military experience of the future emperor Tiberius II Constantine, who is referred to as «great soldier» in some sources. The novelty of the paper is that the military career of Tiberius has not yet been the objective of the research.. The idea to consider the military career of Tiberius was prompted by the fact that almost all the emperors in the last period of the early Byzantine empire — after Justinian I — had military experience and were experts in military arts. The paper analyzes the information sources (Menander Protector, Evagrius Scholasticus, Johannes Biclarensis and Theophanous) depicting the participation of Tiberius in the war with the Avars in order to answer the question: how long and successful was Tiberius’ military command? Despite scarce and contradictory information sources we can conclude that Tiberius, however great his managerial and diplomatic skills could be, should not be regarded as a successful military commander. Tiberius initially chose a non-military career and by the beginning of the war with the Avars he definitely had had no military experience. It is not surprising; therefore, that the only battle attested in the sources, in which he took part as commander-in-chief, ended in the defeat of the Roman army. After a brief military leadership in the war against the Avars, he was not appointed to the position of the commander by Justin II, though he did not lose his patron’s favor.