What is a rapier?

I'm not really being funny, it's an important question. When you start looking at treatises that teach fencing with the kind of weapon we now refer to as a rapier, most authors simply refer to it as "sword" instead of "rapier."

Generally we can make a few distinctions: what-we-now-refer-to-as-rapiers are almost always used in one hand, usually have a fairly complex hilt, usually taper to a sharp point, and usually have a straight blade.

But then there are very odd distinctions made between "rapier" and somehting we now call "sidesword." The only distinction being that sideswords seem to use cuts more than we think rapiers should cut.

But considering "sidesword" was a general word for a sword worn on your person, a "sidesword" is more or less a meaningless distinction, as rapiers were very often worn by gentlemen casually. But so were dusacks, and messers, and longswords, and sabers, and almost every other variety of sword sometime in history.

Interestingly, there are historical fencing sources that use the word rapier. Or at east a variant of it. One of them is the mid 16th century German freifechter Joachim Meyer, who is better known for his longsword teachings, but taught the "rappier" because it was becoming popular as a sidearm for German burghers. Meyer's rapier was a slim blade with a complex hilt that was effective for cutting and for thrusting, and of all the weapons Meyer taught it was likely the most widely used for personal duelling following the 1560s and 70s, where prior to that, the dusack was likely the most popular.

Based on art of the time, and even significantly later than Meyer's time, we see evidence of soldiers wearing what we'd now call "sideswords" along with other battlefield weapons. For instance, this woodcut dated from 1587 shows a pikeman armed with a slim, complex-hilted single handed sword worn at the waist: A Pike-Bearer by Jacob de Gheyn.. Is it a rapier? A sidesword? The same artist shows a nearly identical sword in a 1607 work: from the Exercise of Arms

Well, yes.

There is a popular conception that rapiers either did not cut or were so bad at cutting nobody ever used them to cut. Which is nonsense. Even in the later rapier sources - which, remember, call the sword simply "sword" and don't bother with fine distinctions - which strictly advocate thrusting as the most artful application of the weapon, the authors usually teach how to cut, and how to deal with incoming cuts. Both of which argue that cutting was an extremely common, expected thing to do with a rapier. Such masters are Salvatore Fabris and Nicoletto Giganti. Fabris explained how to cut with the wrist, elbow, and shoulder from both the right and left and above and below, and Giganti gave ample advice about how to deal with an opponent who frequently cuts. Both advocate cutting as a way to deal with multiple opponents.

So were rapiers used in battle? Almost certainly. Soldiers would have carried swords with them they were familiar with and capable of using, and since about the mid 16th century that sturdy, versatile rapier/rappier was extremely common in fencing culture, it would likely have been seen on battlefields just like any other sword.