In 602, the Avars attacked the Antes; this is the last mention of Antes in historical sources. In 615, during the reign of Heraclius (r. 610–641), the whole Balkans was regarded as "Sklavinia" – inhabited or controlled by Slavs. Chatzon led the Slavic attack on Thessaloniki that year. The Slavs asked the Avars for aid, resulting in an unsuccessful siege (617). In 626, Sassanids, Avars and Slavs joined forces and unsuccessfully besieged Constantinople. During the same year of the siege, the Sclaveni used their monoxyla in order to transport the 3,000 troops of the allied Sassanids across the Bosphorus which the latter had promised the khagan of the Avars. In 630, Sclaveni attempted to take Thessaloniki again. Traditional historiography, based on DAI, holds that the migration of Croats and Serbs to the Balkans was part of a second Slavic wave, placed during Heraclius' reign.