The Gepids had held the important city of Sirmium (now Sremska Mitrovica, Serbia) since 536, after taking it from the Byzantine emperor Justinian I.

As it turned out, however, the Byzantine troops neglected to join the Gepids in their fight but kept Sirmium, and although the Avars did not show up either, the Lombards soundly defeated Cunimund's forces in 567.

According to the writings of Paul the Deacon, Alboin killed the defeated king and had his skull converted into a drinking cup known as a scala or patera.

[citation needed] After the Gepids’ defeat, Alboin forced Cunimund’s daughter Rosamund into marrying him.

[1] Cunimund's grim end and Rosamund are mentioned in J. R. R. Tolkien's story "The Lost Road", when the character Alboin asks his father, Oswin Errol, about the origin of his name: …and Oswin told his son the tale of Alboin son of Audoin, the Lombard king; and of the great battle of the Lombards and the Gepids, remembered as terrible even in the grim sixth century; and of the kings Thurisind and Cunimund, and of Rosamunda.