Vespasian was proclaimed at Alexandria on July 1 of the year 69, in Judaea on July 3, and the legions of Syria under Licinius Mucianus quickly followed suit. After a meeting at Berytus to make plans for the war Mucianus set out with an army. The Historiae of Tacitus furnish no details of time or place for defining the itinerary – only the mention of Byzantium.
Meanwhile the Flavian partisans in the Balkan and Danubian lands, Antonius Primus in the forefront, had moved to rapid action. Not content with holding the Julian Alps, they decided, in a council of war held at Poetovio, to launch an invasion of northern Italy. They defeated the Vitellian forces in battle outside Cremona on October 24, they captured Rome on December 20. By good fortune, the first date is correct to within a day, and the second is certified.