It is a day in September around 260 AD on the Rhine river.

It's a September day around AD 260. All seems quiet, but looks can be deceiving.
At the Roman-controlled Rhine river near the colony of Cologne, which has become important, everything seems to be going as usual, as it has for over 100 years. At the fleet fort, a few kilometers upstream, there was unrest, because under the soldier emperor "Trebonianus Gallus" the navy experienced a serious crisis.

Frankish Germanic tribes are camped in the forest on the other side of the Rhine river, and they are restless..

The fleet of the Classis Germanica was stationed in the Cologne area from around 20 AD. The fleet camp came to an end around the middle of the second half of the third century as a result of an attack by Frankish Germanic tribes.