From Wikipedia:
"The use of paired stirrups is credited to the Chinese
Jin Dynasty and came to Europe during the
Middle Ages. "
I have also used Wikipedia, but only when nothing better is available: it makes a good, quick source - usually. In this case, though, the use is of paired
solid stirrups, that provide a solid base for the feet while in the saddle, and it dates specifically from a painting dated to 302 CE in Jin China, but there is another depiction from 200 years earlier showing a Kushan rider using a 'foot rest' stirrup. This implies, though it does not prove, that the Jin stirrup was a development of the Kushan original. This would be consistent with the Chinese adoption of other elements of horsemanship and horse tack from the 'northern Barbarians'.
If you've ever ridden a horse, you'll know that it's fully possible to do so without stirrups, if only because while learning you'll likely have your foot fall out of the stirrup at least once and yet you'll still be able to hold your position on the horse and control the animal. It's going to be much harder without stirrups, especially in combat, but cultures that aren't used to using them will have trained their cavalrymen accordingly.
Actually, the stirrup can be an impediment to certain types of horsemanship. IF you intend to stay firmly upright in the saddle then stirrups are useful. IF, on the other hand, you are going to be dodging about, hiding on one side of the horse or another or using a shield to deflect missiles aimed at one side of the horse or the other, the stirrup just gets in your way. That's why mounted Native North American warriors did not use stirrups (but, the saddles for their women to ride while carrying babies did have stirrups - they knew all about the Technology when it was applicable and useful): they regularly 'dodged' all over the horse. In one early battle with the Nez Perce, one of the premier horse tribes of the Americas, the US Army thought a herd of horses was being driven towards them, because they saw no riders on them - and lost over 20 men to enemy fire from beneath or aside the horses before they knew what hit them. For another example, Roman light cavalry, all pre-stirrup, had a training exercise in which they rode down a path while men on both sides threw padded missiles at them or their horse, and they had to deflect all missiles from both sides using their shield - around, under, and beside the horse. Stirrups would not have helped, and in fact would have made the exercise almost impossible.
What we're calling 'knights' are - it's been pointed out here before - more properly called 'men at arms' (a name which is itself widely used incorrectly in English to refer to armoured infantry). It's not the social rank of knighthood, so Civics isn't the appropriate place for them.
Not quite. The 'knight' did start as a socio-political phenomena, with the
Miles of Charlemagne. It was only after everybody realized that it was much more efficient for the knight to stay home and manage his land/estates and send a substitute equipped as a knight to the muster that the term 'man-at-arms' or the old French term
serjean, meaning a non-nobleman armed like a knight (and from which we get Sergeant) became common. That also coincided in the late Medieval Era with the rise of armies composed almost entirely of Mercenaries, since most of the 'knights' were now, in fact, paid soldiers. Your statement is correct, but only as a development of the original 'noble' knight. Furthermore, the aristocracy always maintained that their prime function was as 'defenders' of the crown and social order, so that aristocratic component of the armies was never absent and in the Industrial Era remained firmly established in the officer corps of most European armies by both custom and Law. In the last years of the French Monarchy, you had to show 4 'quarters' of nobility in your ancestry to become an officer in the infantry or cavalry - if you weren't an aristocrat, only the plebian artillery was open to you
In this the technology is similar to the crossbow: it isn't necessary for the soldier to be effective, but it is easier. People could be effective fighting horsemen with less training so long as they had stirrups - as such they were cheaper to maintain, mercenary bands could be supplied with them, and overall the development of a labour-saving technology resulted in them becoming a more common part of military forces. This is why most mainland Europeans replaced archers with crossbowmen in their armies - the two were roughly as effective as one another but crossbows are much easier to use.
As said, the stirrup is 'easier' only if the rider is doing easy things - sitting upright on the horse, and even then the type of saddle has more influence. As a child, I was taught to ride without using stirrups: I had to learn how to control and manage the horse using hand and leg pressure only before I was allowed to put my feet in stirrups at all. That, in fact (I later learned) was a standard training measure in most European armies from at least the 18th century (see Warnery's
Thoughts on Cavalry, 1754 CE).
As to the crossbow, no question that its adoption had a lot to do with the fact that bowmen had to be raised from childhood practicing while a crossbowman could be trained in a few weeks. Another point, though, was that once metallurgy advanced to the point where steel spring crossbow 'prods' could be manufactured, the crossbow was easier to produce than a longbow, which had to be grown by tailoring a yew tree - and taking years. Ironically (in game terms) the crossbow with its specialized metallurgy was more expensive to produce than an early hackbus' musket which also took very little training time to use, comparatively.
But I repeat: the Stirrup may be associated in popular history with the knight, but it was in no way the essential technological requirement for a mounted armored lance-using horseman: Sarmatians both against and in the Roman Army (
Equites Sarmatii shows up as the title for Roman auxiliary cavalry units throughout the late 2nd - early 5th centuries) and Middle Eastern Cataphracts and Clibanarii, all Pre-Stirrup, all used lances and were fully armored riders.
Even the chivalry of the time knew that: a Knight did not Win His Stirrups, he was said to Win His Spurs, a phrase which is still with us.
