So would a tree-chopping herring be a melee weapon? Or do you leave it in a warm bucket for a few days so it becomes a chemical weapon. Hm.

</Monty Python>

The Spartans like most soldiers of their day did carry a sword...most likely a xiphos or occasionally a kopis. A xiphos is slender, double-edged, and slightly leaf-shaped, with blades mostly around the 60cm mark in length. A very effective stabbing design. The Spartans in particular moved in later days to a much shorter xiphos, with blades as short as 30cm. It was still slender and doubled-edged, not like a Bowie at all. A kopis, less common, is longer, single-edged, and much heavier; optimized for hacking and chopping.

It's important to note that the sword was, again, only a secondary weapon. A Spartan's primary weapon was his dory, or pike, a simple point-on-a-stick. He drew his sword only when his dory was broken, or when the formation collapsed and you were too close to use it. Also significant here is that a Spartan had a huge shield to protect himself with, increasing the usefulness of his small sword.

Battlefield single-edged swords evolved from the xiphos to the falchion, and then abandoned for a time as armor simply got too good for them to be any use. Single edged weapons finally reappeared as the sabre when gunpowder made the wearing of armor obsolete.

Just trying to say, short bladed weapons intended for combat are universally doubled edged, making them daggers (or no-edged, making them stilettoes), and the only single-edged weapons on the field designed to be weapons were long and heavy, beyond even machetes. Which isn't to say that knives can't be used as weapons, or weren't used as weapons. Conscripts, especially, rarely had any standardized arms and brought whatever they could, so you had all manner of pitchforks, mallets, felling axes, hooks, scythes, and knives. But the knife was never intended to be firstly a weapon. The so-called "combat knife" or Bowie pattern is a relatively recent development, and rarely sees use as the weapon of a trained combatant since rifles and even pistols are more effective.

Opinion and semantics perhaps, but there you go.