I was wondering whether the distal taper on swords was deliberately introduced by the smith to make the sword more manuverable, or if it was just a result of lengthning the steel.

A bit of both.

It was clearly a conscious choice on the maker's part, because different swords have very different kinds of distal taper depending on how they were intended to be used (e.g. cutting falchions tend to all be broadly similar, and extremely different from heavy duty thrusting estocs) and some have none at all. But of course drawing out a billet of steel would naturally produce an object of distally varying thickness, which helps reduce the work involved; you can apparently see examples of such naturally occurring distal taper left unadjusted in some 19th Century mass produced tulwar that were forged with no particular care by drawing out a billet in both directions and as a result have their thickest part around the middle of the blade rather than at the hilt...

It's much like the curvature on classical Japanese swords, I'd say - it's technically produced as a side-effect of the differential heat treatment method, but is also actively sought for and controlled by the smith (by means like forging the blade with a curve or counter-curve, pre-treatment, to control the degree and specific shape of the resulting curvature post-treatment).

Distal taper is very well known on early bronze swords, making them fast and lethal weapons. By the time iron came into use, weapon-makers would have thought of distal taper as just one of the obvious features of a sword, like having a hilt. Iron workers simply made blade the shape it needed to be, putting the metal exactly where they wanted it. They were REALLY GOOD at things like that.

Matthew

I agree with Matthew. I would like to add that tapering is the primary reason for many sword’s dynamics, especially in the Middle-Ages/Renaissance. There is a misconception that pommels serve as a counterweight and that they are primarily responsible for balancing a blade, but a great many pommels were hollow. I remember Peter Johnson doing a demonstration where he would add weights to the end of the tang of a blade to demonstrate the effects of pommel weight, but nearly all of the blade’s characteristics were already in place without weights. The pommel was more or less fine tuning, as I recall. So I wouldn’t stop at saying taper was intentional, I’d say it was one of the most important traits a smith considered when designing a sword.

I can give an example of why pommels can't "fix" a heavy blade. I had a client many years ago who got a custom longsword made, and insisted that the point of balance be only 1" along the blade (I would typically balance about 4" along the blade). I made it work - by basically making the pommel large and filling the grip core with lead. And it was HEAVY; any advantage of the point of balance making it lighter in the hand was offset by the whole sword being heavy.

This is why distal taper is critically important to getting the basic behaviours of a blade sorted, and pommels are a combined handstop/fine tuning method. I've handled a few originals, and some pommels are surprisingly small or even hollow, so lighter than people might think; also, medieval cutting swords could balance 8" along the blade, because the user or that particular sword wanted cutting power more than finesse.