Grand Strategy of the Roman Empire, p. 53 and initially defeated an army the Emperor Domitian sent against them, but the Romans were victorious in the Battle of Tapae in AD 88 and a truce was drawn up. Emperor Trajan recommenced hostilities against Dacia and, following an uncertain number of battles, defeated the Dacian general Decebalus in the Second Battle of Tapae in 101 AD. With Trajan's troops pressing towards the Dacian capital Sarmizegethusa, Decebalus once more sought terms. Decebalus rebuilt his power over the following years and attacked Roman garrisons again in 105 AD. In response Trajan again marched into Dacia, besieging the Dacian capital in the Siege of Sarmizethusa, and razing it to the ground. With Dacia quelled, Trajan subsequently invaded the Parthian empire to the east, his conquests taking the Roman Empire to its greatest extent. Rome's borders in the east were indirectly governed through a system of client states for some time, leading to less direct campaigning than in the west in this period. The Kingdom of Armenia between the Black Sea and Caspian Sea became a focus of contention between Rome and the Parthian Empire, and control of the region was repeatedly gained and lost. The Parthians forced Armenia into submission from 37 AD but in 47 AD the Romans retook control of the kingdom and offered it client kingdom status. Under Nero, the Romans fought a campaign between 55 and 63 AD against the Parthian Empire, which had again invaded Armenia. After gaining Armenia once more in 60 AD and subsequently losing it again in 62 AD, the Romans sent Gnaeus Domitius Corbulo in 63 AD into the territories of Vologases I of Parthia. Corbulo succeeded in returning Armenia to Roman client status, where it remained for the next century. Year of the Four Emperors (69 AD) In 69 AD, Marcus Salvius Otho, governor of Lusitania, had the Emperor Galba murderedPlutarch, Lives, Galba and claimed the throne for himself.Lane Fox, The Classical World, p. 542 However, Vitellius, governor of the province of Germania Inferior, had also claimed the thronePlutarch, Lives, Otho and marched on Rome with his troops. Following an inconclusive battle near Antipolis, Vitellius' troops attacked the city of Placentia in the Assault of Placentia, but were repulsed by the Othonian garrison.Tacitus, The Histories, Book 1, ch. 22 Otho left Rome on March 14, and marched north towards Placentia to meet his challenger.