After the death of Nero, governor Galba of Hispania Tarraconensis marched to Rome and became emperor. He had no legitimate claim, and had to earn his claim to the throne. In january 69, the Rhine armies chose governor Aulus Vitellius of Germania Inferior as emperor instead of Galba.
In 68, Galba turned the Roman province of Bosporus into a vassal state again, under king Rhescuporis I.