The victory of the Roman emperor Trajan over the Dacians in back-to-back wars is carved in numerous scenes that spiral around a 126-foot marble pillar in Rome known as Trajan’s Column.

Nerva and Trajan (ruled 96 – 98 AD, 98 – 117 AD) were not born to rule, but were chosen for the job. The results were remarkably successful. Nerva became emperor immediately after Domitian’s ...