Galba's procurator for Belgic Gaul, Pompeius Propinquus, had immediately informed the government of the trouble at Mainz on 1
6 Vitellius'proclamation: Murison 1979(0 378).
January. Galba may well have thought that the animosity of Verginius Rufus' old army was directed not so much against himself, as against Vinius and Otho; 1 January was the day when Galba and Vinius entered upon their joint consulship, and many had assumed (Plutarch tells us) that on that day Otho would be publicly acclaimed as Galba's adoptive son and successor. Even if he had known that the Rhine armies had already gone so far as to proclaim a rival emperor, Galba will still have thought that his chances of regaining the loyalty of these armies would be improved if he showed that there was an alternadve to Vinius and Otho. If he rejected making his nephew Publius Cornelius Dolabella his heir, then it was because he was too fond of him to force him into the position of being a foil to Otho. But Piso mattered less; Galba was willing to put his life at risk. On 10 January he announced his decision to his consilium of amici, and then presented Piso to the praetorians and to the Senate as the new Lucius Sulpicius Galba Caesar.
The adoption of Piso was not so much a matter of indicating who was to be the next emperor, as indicating who was not: Otho. Otho moved swiftly to recover the prize that had as good as been his. Vinius had let him down in the imperial consilium-, Otho had no need of his support now, and Vinius seems not to have been aware of Otho's plans. Galba had alienated the domus Caesaris by executing its freedmen and replacing them with his own; he had alienated certain praetorian tribunes as a result of the coup ascribed to Nymphidius Sabinus, and the rank and file by refusing to pay out the donative of 30,000 sesterces per man promised them by Sabinus in June. (Strictly speaking, a donative had hitherto been a legacy paid out of a deceased Caesar's will as a reward for past loyalty, and Galba had no need to make such a payment on Nero's behalf. But the insulting quip that 'he levied his soldiers, and did not buy them' will have done his popularity little good.) Otho, perhaps with Vinius' backing, had no difficulty in finding supporters amongst the praetorians, the vigiles and the urban cohorts. Early in January Galba himself was frightened enough of the extent of that support to retire several tribunes. They and their friends were easily persuaded to back Otho's coup.
On the advice of his astrologer, Otho finally chose 15 January for his enterprise. He accompanied Galba to a public sacrifice at the temple of Apollo on the Palatine; at the appropriate moment his freedman Onomastus gave the agreed message - that 'the building surveyors are waiting for you at home' - and Otho slipped away to be saluted as emperor by just twenty-three soldiers of the bodyguard. When this small group of supporters reached the praetorian camp, there was no opposition from the officers. Galba's associates — including Vinius, apparently still unaware of Otho's plans - sent to the other troops present in Rome for military support, but without success. A false rumour that Otho had been killed by guards loyal to himself induced Galba to leave the palace in order to give thanks to the gods on the Capitol. As he and his entourage crossed the Forum, it became clear that their hopes were in vain. A small number of praetorians — considerably fewer than those who subsequently claimed the credit — attacked the party. Galba was killed in the Forum by a soldier from one of the Rhine legions. Piso died outside the temple of Vesta, where he had taken refuge. Titus Vinius failed to persuade the man who killed him that he was actually involved in Otho's conspiracy.
The Senate formally recognized Otho as the man who controlled the imperial household and the empire at a meeting held on the same evening. Otho was the first emperor to have seized power as a result of open bloodshed (Claudius had executed his predecessor's assassins). He also soon realized that he was faced with the candidature of a rival emperor on the Rhine. There was an exchange of correspondence with the usurper, and Otho suggested that Vitellius take Vinius' place as his prospective father-in-law. A senatorial embassy was sent to persuade Vitellius to abandon his claim, but it soon became clear that he was not a free agent, and that the Rhine armies would not countenance a peaceful resolution to the conflict.
Nevertheless Otho's regime was popular. He already had the support of the praetorians, and of their officers. For all that he had virtually been Galba's expected successor, he publicly dissociated himself from that unpopular emperor, and instead emphasized his association with Nero: Galba's freedman Icelus and his appointee as praetorian prefect, Cornelius Laco, were both executed. Statues of Nero and Poppaea were restored, and the emperor was acclaimed by the urban plebs as 'Nero Otho'. Any negative features of Nero's last years (when Otho was in Spain) were blamed on the unfortunate Tigellinus, whom Otho now executed. The disappearance of Vinius was a bonus; not only could unpopular decisions taken by Galba be ascribed to him, but Otho was freed from his promise to marry Vinius' daughter. Instead, he proposed to strengthen his claim to be the legitimate paterfamilias of the imperial household by marrying Nero's widow, Statilia Messallina. By representing himself as Nero's successor, and copying his liberality, Otho won the support of the urban population; and he did his best to win supporters among the Senate, not just by inviting senators to dinner at the palace (much to their discomfort when on one occasion the praetorians suspected them of plotting against their emperor), but also by appointing several additional suffect consuls, including Verginius Rufus. Marius Celsus, designated to a suffect consulship for the second half of the year by Galba, was confirmed in it by Otho. Otho himself was formally elected consul, together with his elder brother, Lucius, on 26 January.
Vespasian's elder brother, Flavius Sabinus, was re-appointed to the urban prefecture he had held under Nero.
Like other emperors, Otho made the most of news of military success. The defeat of a Sarmatian raiding party by the legate of Moesia, M. Aponius Saturninus, in February not only gave Otho some of the military prestige which he had hitherto lacked, but also enabled him to tie both the governor and one of his legionary legates, Aurelius Fulvus (grandfather of the emperor Antoninus Pius), to him by bestowing military honours. The governor of Pannonia, L. Tampius Flavianus, was honoured by being given Galba's place among the Arval Brethren; although related to Vitellius, he was to remain loyal to Otho. In any case, most provincial governors had no qualms about recognizing Galba's murderer. Even the governor of Tarraconensis, Cluvius Rufus, at first recognized Otho as emperor. So did the eastern armies: Antioch in Syria minted coins with his image and title. The gold coins issued in Otho's name and proclaiming 'peace throughout the world' were perhaps optimistic, but not absurdly so.7 Only the German and British legions refused to take the oath. (The situation in Britain was confused; the governor Trebellius Maximus seems to have lost control, and fled to Vitellius; but the legionary legates also provided Vitellius with vexilla- tiones of 8,000 men.)