In the year 68 AD, news spread across Britain that Emperor Nero had been ousted and had taken his own life, leading to a civil war in Europe. Following this Rome had four emperors Galba, Otho, Vitellius, and Vespasian. Conflicting army groups put forward rival candidates for the purple. Although the army of Britain did not intervene with its own candidate, vexillations, totalling about 8,000 men, were sent from all three legions to support Vitellius; with the Legio XIV Gemina supporting Otho.
Political discord also arose among the Roman leaders in Britain, with Governor Marcus Trebellius Maximus at odds with many of his commanders, particularly Roscius Coelius of the 20th legion.
Trebellius Maximus, the governor of Britain, had earned by his meanness and cupidity the contempt and hatred of the army, which was further inflamed by the action of his old enemy Roscius Coelius, who commanded the Twentieth legion, and they now seized the opportunity of the civil war to break out into a fierce quarrel. Trebellius blamed Coelius for the mutinous temper and insubordination of the army: Coelius complained that Trebellius had robbed his men and impaired their efficiency.
Gaius Cornelius Tacitus – The Histories, Book One: LX
Marcus Roscius Coelius, commander of Legio XX Valeria Victrix, complained of the deteriorating state of his troops, as they were trained for battle, not idle observation of the natives. This lead to further discontent and into open rebellion. Not being a military man, Marcus Trebellius Maximus lost all authority with the army, which sided with Coelius, and fled to the protection of Vitellius in Germania.
Meanwhile their unseemly quarrel ruined the discipline of the forces, whose insubordination soon came to a head. The auxiliary horse and foot joined in the attacks on the governor, and rallied round Coelius. Trebellius, thus hunted out and abandoned, took refuge with Vitellius.
Gaius Cornelius Tacitus – The Histories, Book One: LX
Marcus Vettius Bolanus appointed Governor (AD69)
The 14th Legion, like the other legions of the Balkans, supported Otho, while their Batavian auxiliaries did not. Unfortunately, the legion did not arrive in time for the first battle of Cremona; only a detachment fought for its emperor, but was defeated with the other Othonian legions.
Vitellius, after his victory over Otho at Badriacum in April 69 appointed Marcus Vettius Bolanus, Governor of Britain. Bolanus took with him the remnants of the Legio XIV, who had supported Otho.
When Bolanus arrived his legions were at half strength and subsquent demands for more troops from Vitellius wer ignored. Discipline had also been lost under the last year of Maximus, and Bolanus lacked the means of restoring it.
The soldiers of the defeated legions still gave Vitellius a good deal of anxiety. Their spirit was by no means broken. They distributed themselves all over Italy, mingling with the victors and talking treason. The most uncompromising of all were the Fourteenth, who refused to acknowledge their defeat. At Bedriacum, they argued, it was only a detachment that had been beaten, the main strength of the legion was not present. It was decided to send them back to Britain, whence Nero had summoned them, and meanwhile they were to share their quarters with the Batavian irregulars, because of the long-standing feud between them. Quartered as they were under arms, their mutual hatred soon broke out into disorder.
Gaius Cornelius Tacitus’ The Histories, Book 2, Chapter 66