Gallus, along with Gaius Suetonius Paulinus and Aulus Marius Celsus, led the assembled troops north from Rome to confront the legions supporting Vitellius near the Po river.
Upon hearing that Spurinna's men were encircled by soldiers loyal to Vitellius, Gallus moved to assist his associate, but stopped at Bedriacum when word reached him that the enemy was driven off after an unsuccessful assault.
[5] Along with Suetonius Paulinus and Marius Celsus, he opposed engaging Vitellius' men immediately, concurring with their advice that Otho would do better to wait until the legions from the Balkans arrived.
[5] When Vedius Aquila, the commander of one of legions supporting Otho, returned to camp and found himself the potential victim of a murderous group of defeated soldiers, Annius Gallus intervened and saved his life.
[7] Werner Eck sees this as evidence that Gallus had been appointed governor of Germania Superior near the end of the year 69 which he held until 72 when he was replaced by Gnaeus Pinarius Cornelius Clemens.