Curved swords as they occurred West of the Ural Mountains seem to accrue as much passion and mythology amongst some people as the Samurai swords of Japan. It is, perhaps, understandable that some of the greatest exponents of that passion and mythology are Hungarians nationalistic enthusiasm leading them to build extravagant structures on shaky foundations.
One common fault in the discussions is the implication that all curved swords can be treated as being the same. Far from it. The variation in styles of sabre can be every bit as much as between a Viking sword and a rapier. It cannot be plausibly suggested that a slightly curved blade, as the earlier ones were, has similar handling characteristics to the (often heavier) very much more curved weapons of the sixteenth century. The most simple observation in that with the former, one can thrust, which is not possible with the latter. Indeed, it can be observed that the type of handle found on such early sabres, slightly offset towards the edge from the line of the blade, and often with a pommel still further offset, seems somewhat more suited to thrusting than to cutting. Of course, there is very little evidence that can be used to reconstruct early sabre techniques, so we are left with impressions gained from handling modern replicas, with the reservations which must be borne in mind. My paramêrion (See under Weapons of the Rômiosi) and another Seljukid style sabre (both reconstructed from artworks, but with carefully calculated weights) were not discernibly different in cutting from straight swords, but could have a slight thrusting advantage if the curve was exploited. Sharp test cutting with a highly curved Indian talwar, in contrast, was once again no more effective in a direct or drawing cut than a straight sword, but became better when the cut was punched.
A primary claim is that sabres came into existence because they are somehow superior to straight swords, especially in the context of mounted warfare. The first question that proposition begs is if that were so, why were they not more widely used?. Even if we entertain the the idea that Westerners did not have the sense to try it for themselves, they came into contact with sabres in various times and places from the ninth century, if not earlier, and yet curved swords were not adopted by Westerners until the fashion for Eastern-style mounted units arose in the eighteenth century. Acknowledging some cultural conservatism, it is still not enough to explain such a neglect of sabres if they had been conspicuously better in any context.
The evidence is nowhere near enough to support the claim that curved swords arose because they work better. To understand the real reason why they were first made, we need to look at where they originated. The first curved swords were used amongst the pastoral peoples of Eastern Europe across to Western Asia. Being semi-nomadic, their craft base is necessarily at least on a smaller scale, and in some ways less sophisticated than the urbanised people who used straight swords. And in that lies the key. The real reason for single edged curved swords is that they are much easier to make than straight swords. Let me explain. And note that these observations are based upon decades of experience as a sword-maker.
To begin, take your refined bloom of iron from the furnace and forge it out into a long, thin, flat thing of about the thickness and width you want.
Now you must create an edge or edges. Once again, this must be done by hammering. Hammering to taper one edge pushes the metal together, squashing it out from the hammer face. Because of the angle of the hammer and resistance of the spine of the bar, most of the metal will push out longitudinally. That spontaneously pushes the bar into a curve as the edge gets wider while the spine remains the same length. Continue that along one edge and voila!, a single-edged curved sword.
This edge forming process creates only quite a gentle curve on a bar of average sword width and thickness, just like the early sabres have. In order to get a greater curve, begin by curving the bar and then hammer the outside of the curve, or if you should want a straight, single-edged sword hammer the inside curve of your blank.
If you should want a straight, double-edged sword, you must repeat the edge hammering process all along the other margin of the work until the same process pushes it to straight.
Hence, the forging process for a single-edged, slightly curved sword only involves half the labour as for a straight, double-edged sword, and less labour than for straight single-edged swords.
The forged blade is not the end of the process by any means. Once it has been cleaned up, it must be hardened and tempered. That is, it must heated until it is red hot, then plunged into some medium (commonly water) to chill it very rapidly. At this stage most carbon steels will be hard, but brittle. To make the blade tough, it must be tempered by heating it again until the polished metal shows a straw or blue colour. The more uniform the heating, quenching and reheating is, the better. The forging process introduces stresses into the metal. The more erratic and repeated the heating during that stage of manufacture, as would often be the case with temporary forges that semi-nomadic people would build, the more stresses result. If one can hold the blade at hardening heat for an extended period prior to quenching, the stresses will often abate, but that is difficult when hardening is done on an open forge. When the blade is quenched, the remaining stresses manifest themselves, bending the blade. Such bending commonly manifests in two planes. If it is perpendicular to the plane of the blade, it is easy to straighten it again once the blade is returned to temper heat. If the bend is parallel to the plane of the blade, it is very much more difficult to change. A straight, double-edged sword that develops that sort of bend may have to go on the scrap pile, thus wasting all that work. With a sword that as always meant to be curved, the fact that it has a little more curve or a little less curve than when it went to be hardened need not be a problem. (But see the comment * appended below)
So, that is the answer. Sabres did not come about because they have some special and superior martial technique. Nor are they necessarily better suited to cavalry. They arose because they are significantly easier and less risky to make with more basic forging and heat treatment facilities.
* The change in curvature can be a problem if you do what I did once and make a scabbard before the blade went for heat treatment. It came back looking much the same, but a slight change in the curve made the scabbard unusable. That heat treatment effect is why the paramêrion shown under Weapons of the Rômiosi is oddly straight in the lower portion of its blade.
© Timothy George Dawson 2019