The falx was a form of
sword - more accurately, a sword which managed to fill the function of both sword and
polearm - used by the
Dacian people, roughly from the fourth century
BCE until the end of the
Dacian Wars at the turn of the second century
CE. The origin of the term is presumably a
cognate with the word
falcata, as the two weapons are similar at basic levels.
To call the falx a sword or a polearm is misleading, considering the elements of each involved in its construction. The basic falx consisted of a long, wooden handle, disproportionately long compared to the hilts of most two-handed swords at up to a meter in length, upon which the blade itself was affixed. The blade of the falx was roughly the same length as the handle, and was slightly curved, with the blade on the curve's inside. The appearance of the falx' blade, as represented in sculpture such as Trajan's Column, is that of a katana on a tremendous handle with the wrong side sharpened.
The falx was not a subtle weapon. Typical Dacian usage of it seemed to involved pinning down enemy formations with massed infantry before sending out falxmen in a half-berserk charge into the enemy flank. The falx was designed to be swung, and swung hard, and worked best with open-order infantry in much the same way that axes or claymores would be used. The shape of the blade permitted it to make vicious draw cuts, even over shield walls, and the length of the blade and handle permitted swings to be made at relatively safe distances. This angered the Romans, who were forced to rely on the short gladius as their primary weapon, to no end.
The falx was a terrifying weapon, able to deliver absurd amounts of force in its swings, and Roman records of the Dacian Wars speak of legionaries reacting in surprise at how quickly the sword could sever limbs or heads. So dangerous was the falx that legions deployed in Dacia had to redesign their armor; the lorica segmentata, normally sleeveless, recieved an extended set of bands to protect the soldiers' right arm, and Roman helmets recieved a pair of reinforcing crossbars to survive the falx's blows. Although there was little left of Dacian culture or weapons after the second Dacian War, the lessons delivered by the falx would remain, quite literally, on the minds of Roman soldiers for the next two centuries, and the basic idea, albeit in significantly different forms, would form the basis of the great polearms of European armies through the next millenium and a half.