Year of the Four Emperors

The Year of the Four Emperors, AD 69, was the first civil war of the Roman Empire, during which four emperors ruled in succession, Galba, Otho, Vitellius, and Vespasian. It is considered an important interval, marking the change from the Julio-Claudians, the first imperial dynasty, to the Flavian dynasty. There were several rebellions and claimants, with shifting allegiances and turmoil in Rome and the provinces.

In 68, Vindex, legate of Gallia Lugdunensis, revolted against Nero and encouraged Galba, governor of Hispania, to claim the Empire. The latter was proclaimed emperor by his legion in early April. He was notably supported by Otho, legate of Lusitania. Soon after, the legate of a legion in Africa, Clodius Macer, also rebelled against Nero. Vindex was defeated by the Rhine legions at the Battle of Vesontio, but they too rebelled against Nero. On 9 June 68, Nero took his own life after being declared a public enemy by the Senate, which made Galba the new emperor. Galba was unable to establish his authority over the Empire, as several of his supporters were disappointed by his lack of gratitude. He especially adopted Piso Licinianus as heir (Galba was childless and elderly), instead of Otho, who, it had widely been assumed, would be chosen. Angered by this disgrace, Otho murdered Galba on 15 January with the help of the Praetorian Guard, and became emperor instead. Unlike Galba, he rapidly earned considerable popularity, notably by bestowing favours and emulating Nero's successful early years.

Otho still had to face another claimant, Vitellius, who had been acclaimed by the legions of the Rhine on 1 January 69. Vitellius won the First Battle of Bedriacum on 14 April, defeating the emperor. Otho took his own life the next day, and Vitellius was appointed emperor by the Senate on 19 April. The new emperor had little support beyond his veterans from the German legions, though. When Vespasian, legate of Syria, made his bid known, he received the allegiance of the legions of the Danube as well as many former supporters of Galba and Otho. After his acclamation in Alexandria on 1 July, Vespasian sent his friend Mucianus with a part of his army to fight Vitellius, but the Danubian legions commanded by Antonius Primus had not waited for Mucianus and defeated Vitellius' legions at the Second Battle of Bedriacum on 24 October. Vitellius was killed by a mob on 20 December. Mucianus arrived several days after and swiftly secured Vespasian's position in Rome (Primus had acted independently from him).

The death of Vitellius did not end the civil war, as the Rhine legions still rejected the rule of Vespasian and the new Flavian dynasty. Some Batavi provincials led by Civilis had fought them since Vitellius' acclamation. In 70, the new regime finally won the legions' surrender after negotiations, mainly because they lacked an alternative to Vespasian. Later, the new regime distorted the events—especially through the writings of the historian Tacitus—to remove the embarrassment of having relied on the Batavi to fight Roman legions. The Batavi were therefore said to have revolted against Rome, and the events called the Revolt of the Batavi.

The end of Nero's reign (54–68) was marked by political trials and plots, such as the Pisonian conspiracy in 65, showing the disenchantment of the senatorial elite towards the Emperor. In the winter of 67–68, Gaius Julius Vindex, the legate of Gallia Lugdunensis, looked for support among other governors and administrators to start a revolt against Nero. Aware of his relatively humble origins, Vindex did not covet the Empire for himself, nor did he name a candidate, probably to maximise his chances of finding someone interested. Plutarch tells that the people reached by Vindex forwarded his letters to Nero, except one, his southern neighbour Servius Sulpicius Galba, the governor of Hispania Tarraconensis, the largest Spanish province. In mid-March 68, Vindex proceeded with his plan and raised an army composed of Gallic warriors, which cut short his attempts to win over the officers of the seven legions posted on the Rhine, whose soldiers would not accept fighting alongside Gauls. Vindex turned to Galba, the only man who had not denounced him to Nero.

In early April 68, Galba accepted Vindex's proposition and was acclaimed emperor in Carthago Nova (now Cartagena, Spain). He rapidly received support from officials of Baetica and Lusitania, the other two Iberian provinces, who provided him with the money to raise the VII Galbiana, a second legion, in addition to the VI Victrix based in Galba's province.

Vindex had to besiege his former capital, Lugdunum, as its citizens were particularly devoted to Nero, which led Lucius Verginius Rufus, the governor of Germania Superior, to march on Vindex. He besieged Vesontio, capital of the Sequani, a tribe that supported Vindex, who had to leave the siege of Lugdunum to come to their aid. Before Vesontio, Verginius and Vindex had a talk, during which they agreed to unite their forces against Nero. Verginius' legions ignored the agreement and charged the unprepared troops of Vindex, of whom up to 20,000 died, while Vindex committed suicide. Soon after, the Rhine legions proclaimed Verginius emperor but he refused to accept. The soldiers were motivated by their hatred of Galba, as they had not forgotten his term as governor of Germania Superior in 39–41, during which he harshly repressed the legions that had supported the rebellion of Lentulus Gaetilicus in 39.

In Rome, Nero was unable to organise resistance to Galba's claim and was even thinking about fleeing to Egypt. The decisive move came from Nymphidius Sabinus, deputy prefect of the Praetorian Guard, who convinced his men to abandon Nero, by promising that Galba would give each of them 30,000 sesterces (equivalent to 10 years of wages), while he expected to be rewarded by the new emperor. On 9 June 68, the Senate declared Nero enemy of the state and proclaimed Galba emperor, which prompted Nero's suicide.