clergy and flock to the island of Grado in Byzantine-controlled territory. From Aquileia, Alboin took the Via Postumia and swept through Venetia, taking in rapid succession Tarvisium (Treviso), Vicentia (Vicenza), Verona, Brixia (Brescia) and Bergomum (Bergamo). The Lombards faced difficulties only in taking Opitergium (Oderzo), which Alboin decided to avoid, as he similarly avoided tackling the main Venetian towns closer to the coast on the Via Annia, such as Altinum, Patavium (Padova), Mons Silicis (Monselice), Mantua and Cremona. The invasion of Venetia generated a considerable level of turmoil, spurring waves of refugees from the Lombard-controlled interior to the Byzantine-held coast, often led by their bishops, and resulting in new settlements such as Torcello and Heraclia. Alboin moved west in his march, invading the region of Liguria (north-west Italy) and reaching its capital Mediolanum (Milan) on 3 September 569, only to find it already abandoned by the vicarius Italiae (vicar of Italy), the authority entrusted with the administration of the diocese of Annonarian Italy. Archbishop Honoratus, his clergy, and part of the laity accompanied the vicarius Italiae to find a safe haven in the Byzantine port of Genua (Genoa). Alboin counted the years of his reign from the capture of Milan, when he assumed the title of dominus Italiae (Lord of Italy). His success also meant the collapse of Byzantine defences in the northern part of the Po plain, and large movements of refugees to Byzantine areas. Several explanations have been advanced to explain the swiftness and ease of the initial Lombard advance in northern Italy. It has been suggested that the towns' doors may have been opened by the betrayal of the Gothic auxiliaries in the Byzantine army, but historians generally hold that Lombard success occurred because Italy was not considered by Byzantium as a vital part of the empire, especially at a time when the empire was imperilled by the attacks of Avars and Slavs in the Balkans and Sassanids in the east. The Byzantine decision not to contest the Lombard invasion reflects the desire of Justinian's successors to reorient the core of the Empire's policies eastward. Impact of the migration on Annonarian Italy The impact of the Lombard migration on the Late Roman aristocracy was disruptive, especially in combination with the Gothic War; the latter conflict had finished in the north only in 562, when the last Gothic stronghold, Verona, was taken. Many men of means (Paul's possessores)