In the closing days of the Western Roman Empire, the military was more defensively reconfigured into a cavalry force designed to protect the Empire. Their main weapon of the infantry was the short sword, the gladius, was replaced with a longer sword with a rounded tip. This so cavalry would not would themselves when fighting from horseback.
In the story I take an author’s prerogative and use the gladius. While cavalry does appear when Tulli, Peta, Livia, and the hound, Ursus travel to Attila’s walled city, I did not use the cavalry sword as the story did not need it.