I've been working with a lot of wire lately and it got me thinking about the stuff in general. I know at one point pins we're used as a sort of ersatz currency (at least I think I know this) so I imagine it was, at one time, relatively hard to come across. Did that only change with the industrial revolution or, it being such useful stuff, was it sooner than that?
Modern wire is produced in about the same way that it has been for the last roughly one thousand years or so, by drawing through a progression of dies (chunks of metal with specifically shaped and sized holes in them). You start with a larger sized loop of wire (or a strip of thin metal), you then modify a small section of one end of it so that it can fit through a die (which could involve hammering, using a file, swaging, or any number of other comparatively labor intensive techniques). Then you pass that end through the die and pull the rest of the larger sized wire through using a great deal of force. The hole of the die is shaped to funnel the wire into a smaller diameter as it passes through, then you simply use multiple passes through successively smaller dies to achieve the wire size you desire (at each step the wire getting thinner and the loop getting much longer). Since the industrial age this has all been backed by powered machinery, in the middle ages it would have been on a smaller scale and often human powered (though frequently with the aid of equipment and machines to apply significant mechanical advantage and convenience to the process and in some cases with the aid of water wheels).
A somewhat similar technique was used much earlier: pulling very thin and narrow pieces of metal through small holes to cause the metal to roll up into a tube in the shape of the hole. Additionally, you can push material (strips of metal for example) into a groove or between two pieces of material with grooves to form it into a specific shape, potentially a wire, this is known as swaging. These techniques are around 4000 to 5000 years old (maybe older) and date back to the early Bronze Age. Most ancient uses of metallic wire was in jewelry, it wasn't until the medieval period that wire production techniques started allowing for a much greater diversity of uses (including in manufacturing chain mail).
Wire is over 5,000 years old. The earliest known wire was forged, basically with the metal just being hammered into long thin bits. Making wire purely by forging is OK for short pieces, but it's hard to make long and/or uniform pieces of wire like this. It is possible to forge longer pieces. This was usually done by the metal being forged into a sheet, and then cut into narrow strips, and these strips then being forged to a round cross-section. This technique is very old, being described in the Bible, in Exodus 39:3:
And they did beat the gold into thin plates, and cut it into wires
The strips can be twisted before the final forging. These methods were usually used for gold wire - gold is very malleable, and can be hammer-welded easily, so the twisted bits get welded in the forging process.
The usual modern method of wire-making is drawing, where the metal is pulled through a hole slightly smaller than its width. The starting piece of metal can be forged into a thin rod, or (especially with gold) a twisted strip (as for the second forged wire method above) can be used. As the metal is pulled through the hole, it is forced to become smaller:
It can be drawn through a series of successively smaller holes, becoming smaller each time, until the desired size is reached. The piece of material with the hole is called a draw plate; the hole is a die, and a draw plate can have multiple dies. Different materials can be used, but the die needs to be harder than the metal being made into wire. It is much easier to produce uniform wire by drawing than by either of the first two techniques. Wire-drawing was already being used in ancient Egypt, to produce gold wire. The Egyptian method started with the second technique above, starting with a sheet, cutting it into strips, and twisting them. These twisted ribbons where then drawn through the die.
We don't know when drawing started being used for iron wire. The oldest European draw plate used for iron wire I know of is a 9th century Viking find. One famous use of wire by the Vikings was for making mail armour, but mail is much older than the Vikings, having been used by the Romans, and appears to have been invented by the Celts before them. Whether they used drawn wire is unknown, but it is possible. The process is illustrated in Medieval art:
Thicker wire can be drawn more readily using a winch:
and even thicker wire using water-power:
(The last two illustrations are from http://combatarchaeology.org/artefact-of-the-month-the-mail-chausses-of-molledalen-buskerud/ which discusses the making of mail armour.)
The big advance which led to wire rope was increasing mechanisation. First, the increasing use of machinery made the wire-drawing process faster and cheaper, and mechanised roll-forging made it faster and cheaper to produce the round pieces of iron to start the drawing process.
Video of Medieval-style hand-drawing: https://www.britannica.com/video/180089/visit-museum-Germany-Altena
Modern mechanised drawing through a series of dies: https://www.youtube.com/watch?v=wlWkz9hjASo
In summary, Medieval technology is easily enough for hand-drawn iron wire.
Further reading:
Brian D. Newbury and Michael R. Notis, "The History and Evolution of Wiredrawing Techniques", JOM 56(2), 33-37 (2004)
(This is a slightly edited version of an older answer.)
