Several of the Nerva-Antonine Dynasty emperors were known for their notable military successes.

Trajan and the Dacian Wars

After Nerva’s short rule, his adoptive heir, Trajan, a popular military leader, ruled as emperor from 98-117 CE. Officially declared by the Senate as optimus princeps (“the best ruler”), Trajan is remembered as a successful soldier-emperor who presided over the greatest military expansion in Roman history, leading the empire to attain its maximum territorial extent by the time of his death.

The Dacian Wars (101-102, 105-106) were two military campaigns fought between the Roman Empire and Dacia during Roman Emperor Trajan’s rule. The conflicts were triggered by the constant Dacian threat on the Danubian Roman Province of Moesia, and also by the increasing need for resources in the economy of the Roman Empire.

Dacia, an area north of Macedon and Greece, and east of the Danube, had been on the Roman agenda since before the days of Caesar, when they defeated a Roman army at the Battle of Histria. In 85 CE, the Dacians swarmed over the Danube and pillaged Moesia, and initially defeated the army that Emperor Domitian sent against them. The Romans were defeated in the Battle of Tapae in 88, and a truce was established.

Emperor Trajan recommenced hostilities against Dacia and, following an uncertain number of battles, defeated the Dacian King Decebalus in the Second Battle of Tapae in 101. With Trajan’s troops pressing towards the Dacian capital, Sarmizegetusa Regia, Decebalus once more sought truce terms. Decebalus rebuilt his power over the following years and attacked Roman garrisons again in 105. In response, Trajan again marched into Dacia, besieging the Dacian capital in the Siege of Sarmizegetusa, and razing it. With Dacia quelled, Trajan subsequently invaded the Parthian empire to the east, his conquests expanding 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 conclusion of the Dacian Wars marked a triumph for Rome and its armies. Trajan announced 123 days of celebrations throughout the Empire. Dacia’s rich gold mines were secured, and it is estimated that Dacia then contributed 700 million Denarii per annum to the Roman economy, providing finance for Rome’s future campaigns, and assisting with the rapid expansion of Roman towns throughout Europe.

The two wars were notable victories in Rome’s extensive expansionist campaigns, gaining Trajan the people’s admiration and support. The conclusion of the Dacian Wars marked the beginning of a period of sustained growth and relative peace in Rome. Trajan began extensive building projects and became an honorable civil leader, improving Rome’s civic infrastructure, thereby paving the way for internal growth and reinforcement of the empire as a whole.

Hadrian and Hadrian’s Wall

Despite his own great reputation as a military administrator, Hadrian’s reign was marked by a general lack of documented major military conflicts, apart from the Second Roman-Jewish War. Hadrian had already surrendered Trajan’s conquests in Mesopotamia, considering them to be indefensible. In the East, Hadrian contented himself with retaining suzerainty over Osroene, which was ruled by the client king, Parthamaspates, once client king of Parthia under Trajan.

Hadrian’s abandonment of an aggressive policy was something the Senate and its historians never forgave: the fourth century historian, Aurelius Victor, charged him with being jealous of Trajan’s exploits and deliberately trying to downplay their worthiness. It is more probable that Hadrian simply considered that the financial strain to be incurred through keeping a policy of conquests was something the Roman Empire could not afford. Proof of this is the disappearance during his reigns of two entire legions. Also, the acknowledgement of the indefensible character of the Mesopotamian conquests had perhaps already been made by Trajan himself, who had disengaged from them at the time of his death.

The peace policy was strengthened by the erection of permanent fortifications along the empire’s borders. The most famous of these is the massive Hadrian’s Wall in Great Britain, built on stone and doubled on its rear by a ditch (Vallum Hadriani), which marked the boundary between a strictly military zone and the province. The Danube and Rhine borders were strengthened with a series of mostly wooden fortifications, forts, outposts, and watchtowers, the latter specifically improving communications and local area security.

To maintain morale and prevent the troops from becoming restive, Hadrian established intensive drill routines, and personally inspected the armies. Although his coins showed military images almost as often as peaceful ones, Hadrian’s policy was peace through strength, even threat, with an emphasis on discipline, which was the subject of two monetary series.

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