Spatha, cAD300

[Urselius]

A good indication of the time of the adoption of bar-shaped guards on Roman swords is the depiction of such on the ivory diptychs of Honorius and Stilicho. The second leaf of the Honorius ivory shows an eagle hilted sword so we can be fairly sure that the other forms show Roman swords rather than ones of barbarian manufacture. So, by the early decades of the 5th century Roman swords had evolved into an Early Medieval-type form.

Interestingly, the swords from the diptychs show some unique features relative to "Germanic" sword types. As well as a second bar at the pommel, Honorius' sword also surmounts this with a sphere or wheel-shaped element. Stilicho's sword does not have a bar at the pommel but seems to swell out from the grip into a fluted expansion, though this too is surmounted by a ball or circular element.

The earlier Germans produced copies of the Roman gladius shortsword, I do not think that they suddenly became weapons innovators in the 3rc-4th centuries. I suspect that both the Germanic peoples and the Romans were adopting sword types introduced by the various Iranian Steppe peoples (Sarmatians, Alans etc.) who came into contact with both these cultures at much the same time.