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.

In 110 AD, Trajan sent Pliny to Bithynia (part of present-day Turkey) to investigate corruption there. He appears to have died a few years later. His lasting fame, however, comes from the nine ...