Swords are one of the most misunderstood tools around. From bad descriptions in books (i.e., "as the Viking lifted his sword, so long and heavy an average man could not wield it") to junk handled at stores, people have a lot of incorrect ideas about them.
I'll concentrate mostly on European swords, as that's where most of my knowledge lies. To hit some categories:
A: Size In the medieval period, the average broadsword fit in a range of 32 to 36 inches overall length, pommel to point.
B: Weight These same swords weighed in a range from 2 to 3 pounds. Doesn't sound like much, but try this; take a piece of rebar three feet long, weighing 3 pounds, find a dead tree or heavy fence post, and start swinging. It won't be long before your tongue's hanging out and your arm & shoulder is on fire. This is work, no way around it.
C: Materials Steel for the blade, of course, but quality could range from superb to crap, depending on who made it and where. Most sword blades were made in one of a half-dozen cutlery centers in Europe, places where iron deposits, forests for charcoal, and water for transport and to run waterwheels were available. Any good blacksmith could turn out a knife, an axe or spearhead; standard tools everywhere, and the spear was a tool of the hunter as well as a weapon. But a sword...
For a quality piece, a sword demands the best of materials & workmanship. It has to be tough enough not to break on repeated impacts, hard enough to hold a decent cutting edge, and light enough to swing & thrust. One reason a sword was a tool of noblemen, and came to be seen in many cases as much a badge of rank as a weapon, was the cost of making it. In a time when nobody could make steel in any real quantity of consistent quality, knowledge was required. Take a bar of steel that you may have made yourself from iron by case-hardening. Forge it to a square or rectangular bar, then fold it, and weld it. Draw it out longer, and fold/weld again, and keep doing it. Get sloppy, you burn the piece and ruin it. Take too many heats to do the number of folds you need, and you lose a lot of stock(some of the stuff you see on an anvil after hammering a piece is scale; hot iron or steel combines with oxygen in the air and forms it, so every time you work a piece you lose a little bit of your stock). When it's ready you have to shape it into the blade, then harden & temper it /both very tricky with a sword/, and then finish grind and polish it. If a weld didn't quite take, it might not show until you harden it, when it cracks; or it may show up as a flaw when you polish it, either may completely ruin the blade.
Our ancestors wouldn't have known what we mean by metallurgy, but they knew how to do things. In the early 1900's, someone in England found a Saxon warchief's grave, complete with all the stuff he'd been buried with, including his sword. It was badly corroded, of course. Later, someone had the idea to x-ray it, and wonder followed. This thing was made as follows:
The center was a series of square bars of wrought iron, with twists at regular intervals, the bars stacked with opposing twists together and welded to make the body;
The edge was a piece of pattern-welded steel, made as described above, shaped to match the forged and ground profile of the body, then welded on, a section at a time.
The piece was filed and ground to profile; the fuller- groove- down the center was chiseled out, then ground smooth & even; the bevels to the edges ground & filed, all a little oversize; and the tang, where the guard, grip & pommel would fit on, was cleaned & shaped.
As it was now, it wouldn't work well, because it would bend on impact (remember the iron core?), so they made up a mix someone, somehow, had worked out; charcoal, bone meal, pigeon droppings, other carbon-bearing stuff; and coated the blade with it. Then it was put in a clay chest, on a bed of sand and with other sand poured over, then the chest sealed, and placed into a furnace. Kept at about 1500 degrees F long enough, a wonderful thing happened; the surface of the iron core became steel, and a little more carbon soaked into the edge /remember I mentioned case-hardening?/. When it piece was pulled out of the chest it was quenched- hardened-, tempered, ground to final shape and polished, and then washed with acid. Different layers in the blade were shown by the acid etching, and those opposing twists in the iron bars now became chevrons running up and down the blade.
Now you have a sword blade with a soft iron core, extremely tough; a strong, springy steel skin over it; and an edge hard enough to cut and tough enough not to break. A piece of artistry in steel as fine as you'll ever see. And made as a working tool; no chieftain with a working brain would carry a sword or axe, no matter how fancy, that wouldn't work.
If you get a chance, look up the Sutton Who gravesite and sword.
I cannot imagine, with work like this in the past, why some people think our ancestors were all a bunch of fools.