The two Dacian Wars (101–102, 105–106) during Roman Emperor Trajan's rule are triggered by the constant Dacian threat on the Danubian Roman Province of Moesia and by the increasing need for resources of the economy of the Roman Empire.

Dacia, an area north of Macedon and Greece and east of the Danube, has been on the Roman agenda since before the days of Caesar, when they defeated a Roman army at the Battle of Histria.

The Dacians had swarmed over the Danube in CE 85, pillaged Moesia, and initially defeated the army that Emperor Domitian had sent against them.

The Romans had been victorious in the Battle of Tapae in 88 and a truce had been established.

Emperor Trajan recommences hostilities against Dacia and, following an uncertain number of battles, defeats 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 seeks terms.

Decebalus rebuilds his power over the following years and attacks Roman garrisons again in 105.

In response, Trajan again marches into Dacia, besieging the Dacian capital and razing it.