The conflicts were triggered by the constant Dacian threat on the Danubian province of Moesia and also by the increasing need for resources of the economy of the Empire.

[11] At the time, Rome was suffering from economic difficulties largely brought on by military invasions throughout Europe and in part due to a low gold content in Roman money as directed by Emperor Nero.

The Roman offensive was spearheaded by two legionary columns, marching straight to the heart of Dacia, burning towns and villages en route.

This bridge, probably the biggest at that time and for centuries to come, was designed by Apollodorus of Damascus and was meant to help the Roman army advance faster in Dacia in case of a future war.

According to the peace terms, Decebalus got technical and military reinforcement from the Romans in order to create a powerful allied zone against the dangerous possible expeditions from the northern and eastern territories by hostile migrating peoples.

Faced with large numbers of allied tribes, the legions struggled to attain a decisive victory, resulting in a second temporary peace.

Eventually, goaded by the behaviour of Decebalus and his repeated violations of the treaty, Rome again brought in reinforcements, took the offensive and prevailed in 105.

[13] The final decisive battle took place near the walls of Sarmizegetusa, presumably during the summer of 106, with the participation of the legions II Adiutrix and IV Flavia Felix and a detachment (vexillatio) from VI Ferrata.

One hundred thousand male slaves were sent back to Rome; and to discourage future revolts, legions XIII Gemina and V Macedonica were permanently posted in Dacia.

The conquered half (southern) of Dacia was annexed, becoming a province while the northern part remained free but never formed a state.

The two wars were notable victories in Rome's extensive expansionist campaigns, gaining Trajan the people's admiration and support.