Trajan ruled when the Roman Empire reached its greatest territorial extent.
Marcus Ulpius Traianus became emperor in 98 CE and expanded Roman control through major campaigns. His conquest of Dacia, completed after wars in 101–102 and 105–106, brought valuable gold resources and created a new Roman province north of the Danube.
In the east, Trajan annexed territories connected with the Nabataean kingdom and campaigned against the Parthian Empire. At the height of his reign in 117 CE, Roman territory covered an area larger than at any other point in the empire’s history.
Trajan’s successor, Hadrian, abandoned some eastern conquests and emphasized consolidation rather than continued expansion. This change is why Trajan is associated with the empire’s maximum extent, while Hadrian is remembered for strengthening and defining its frontiers.