Nero became a young emperor of the Roman Empire in 54. His regents ruled for him in the first years. In 54/55, the war in Armenia was won by the Parthians. Rhadamistus had to flee the country and was replaced by Tiridates. The Romans had to quel a revolt of Venutius of the Brigantes in the mid 50s. Lesser Armenia became independent from Pontus under king Aristobulus in 55. In 56, Alpes Cottiae was annexed by the Roman Empire.
In 58-59, Gnaeus Domitius Corbulo reconquered Armenia for the Roman Empire, replacing Tiridates I with Tigranes VI as king.
Governor Gaius Suetonius Paulinus of Britain conquered the island of Mona in 60, a bulwark of Celtic druids and refugees against Roman rule.
The Iceni and Trinovantes revolted under queen Boudicca against Roman rule in Britain in 60/61. Governor Paulinus made an end to this and annexed territory of the Iceni.
Armenian forces invaded the Parthian province of Adiabene in 61. King Vologases I of the Parthian Empire responded by conquering Armenia, putting Tiridates back on the Armenian throne. In 62, the Romans under governor Lucius Caesennius Paetus of Cappadocia were defeated at the battle of Rhandeia. Afterwards he made peace with the Parthians and accepted their claim on Armenia.
When the news about the peace treaty with the Parthians reached Rome, emperor Nero was surprised, because Paetus had lied about the situation, depicting it in a positive light. Nero gave command of a large army in the east to governor Corbulo of Syria. This army was too large for the Parthians to deal with and they were ready for peace. To the Parthian surprise, Nero accepted Tiridates as king of Armenia, in exchange for paying homage as vassal to the Roman Empire.
Nero increased Roman defense in the east. Bosporus (63) and Pontus (64) were annexed, and Roman troops were placed in Colchis, Caucasian Iberia and Caucasian Albania, on the northern borders of Armenia.
In 66, the Jews in Judea revolted against Roman rule. Governor Cestius Gallus of Syria send an army to Judea, which was defeated by the rebels at the Battle of Beth Horon (66). Nero send Titus Flavius Vespasianus to Judea to reconquer it. In 68, Vespasian had conquered northern Judea, when a civil war broke out in the Roman Empire.
The civil war started with the rebellion of governor Gaius Iulius Vindex of Gallia Lugdunensis in 67/68, who was supported by governor Servius Sulpicius Galba of Hispania Tarraconensis. The Roman Rhine army of Germania Superior and Germania Inferior under Lucius Verginius Rufus defeated Vindex at the battle of Vesontio in 68, killing Vindex. But, antipathy against Nero was rising. The Rhine army wanted Vindex to become emperor, but he refused. Nero lost support in Rome. He fled and killed himself, when the news came that the senate had ordered his death penalty.