Traditionally, scholarship has placed the arrival of the White Croats from Great/White Croatia in the 7th century, primarily on the basis of the later Byzantine document "De Administrando Imperio". As such, the arrival of the Croats was seen as a second wave of Slavic migrations, which took over Dalmatia from Avar hegemony. However, as early as the 1970s, scholars questioned the reliability of Porphyrogenitus' work, written as it was in the 10th century. Rather than being an accurate historical account, "De Administrando Imperio" more accurately reflects the political situation during the 10th century. It mainly served as Byzantine propaganda praising Emperor Heraclius for repopulating the Balkans (previously devastated by the Avars) with Croats, who were seen by the Byzantines as tributary peoples living on what had always been 'Roman land'.