This is JRR Tolkien's own creation, an oral telling of Beowulf, parsed down and meant for a camp fire. I include some of his, and Christopher Tolkien's notes, in the reading.
It is near the end of Winter, 52 BC.
Germans, goaded by the Gaul Aduataca, are attacking the winter camp of Cicero, one of Caesar’s trusted commanders...
Julius Caesar, after defeating the German Warlord Ariovistus, finds himself contending with a new foe in the Belgae to the north, near what is now Calais in France...
56AD: Julius Caesar has just built a bridge over the Rhine for his entire army, crossed that river, and defeated one of the Germanic tribes that had been vexing the Gauls. Now, he turns his eyes to Britain...
It is now the year 53 BC. Caesar has put down a Gaulish rebellion in the east, and quashed the Nervii tribe. He moves to deal with Ambiorix, and the Treviri.