As allies of the Byzantine Empire of Justinian I (r. 527–565), the Avars had obtained a grant of gold to crush other nomads – the Sabirs, Utigurs, Kutrigurs and Saragurs – in the lands later known as Ukraine, a task they accomplished to the emperor's satisfaction.
The Avars, traditionally a nomadic people, desperately needed both shelter and pasture for their livestock, but the route to Pannonia was blocked by impassable mountains covered with thick forests: the Carpathian range.
In the meantime large numbers of Slavs settled in Pannonia in the wake of the Avars; and in 568 Alboin and his Lombards deemed it wise to move to the half-ruined but promising lands of Italy where they would establish a long-lasting kingdom.
They concluded however a treaty with the Avar Khagan allowing them to reenter parts of Pannonia and Noricum (Austria) if they chose to do so in the future; they then departed with large numbers of the vanquished Gepids and a host of other Germanic tribes.
[citation needed] Repeated, massive defeats shook the Avaro-Slavic hordes as strong organized Byzantine armies penetrated north of the Danube into Wallachia, and eventually, under general Priscus, crushed the enemy along the river Tisza in the very heart of Pannonia.