At the end of the 3rd century AD, a new typology of helmets appears in the Roman army, a type that will be used at least until the 5th century: the so called “ridge helmets” – a name given cause of the middle raised band that unites the two halves of the skull.
It is often thought that ridge helmets were of poorer quality and less robust than previous Roman helmets, the skull of which was made from a single piece of metal (es. Imperial Gallic and Italic, Niederbieber helmets, etc.), in particular concerning the “lighter” versions of the ridge helmets. However, these considerations are not totally true.
In fact, generally speaking, ridge helmets cover the same areas that were protected by previous helmets, and in some case they could be even more protective – for instance, the “heavy” types of ridge helmets often have enclosing cheek guards and a nose guard.
Also, the fact that the skulls of the ridge helmets are made by more pieces doesn’t make them automatically less resistant. In fact, helmet skulls made from a single piece of metal have some weaker points where the metal sheet is thinner – an inevitable consequence of hammering metal. Having the skull made by more pieces minimizes this problem, and the central ridge makes the point that takes more hits even more robust – moreover, some types of “heavy” ridge helmet also have additional lateral metal bands, that makes the skull even more resistant.
It’s generally acknowledged that ridge helmets originated in the East, in the border area between the Roman Empire and the Sasanian Empire. A probably Sasanian helmet found in the site of Dura Europos, dated to the 3rd century AD, was identified as the “prototype” of the ridge helmets.
Ridge helmets could be categorized under two main types: a “light” one, and a “heavy” one. “Light” ridge helmets have relatively narrow cheek pieces and no protection for the face, while the “heavy” ones usually feature very enclosing cheek pieces and nose guards. “Light” ridge helmets have been classified as infantry helmets, while “heavy” ridge helmets have been considered as cavalry helmets. However, even if we know for sure that some “heavy” ridge helmets did really belong to cavalrymen – we are sure of this cause of inscriptions found on some helmets –, there isn’t actually any element that could determine such a clear distinction of use between the two types.
“Light” ridge helmets always have ear-holes, while on “heavy” ones this feature is most of the times missing. However, Romans also experimented other solutions, like the ridge helmets of the Koblenz typology: these helmets have metallic plates with holes in the area of the ears, so uniting protection and the possibility to hear clearly.
Various specimen of ridge helmets were decorated – by gildening or silvering, by incised or embossed decorations (both on the skull and on the cheek pieces), by placing rivets on the crest and on the skull of the helmet, and even by precious stones in the richest examples.
Another way to decorate the helmet was by using a crest. These could have been made of organic materials – as could be seen mainly on iconographical sources – or, particularly in the 4th century, from metal. The latter ones often sported a decorative front plate that featured the Christogram.