Dave Long wrote:It only makes sense that spanish riders and horses would be well adapted to rapid changes of direction. Mounted stock work (like war) requires rapid changes of direction to deal with bovines (respectively opponents) who are doing their best to get outside your OODA loop, and the spanish historically not only spent a fair amount of their time fighting, but also running cattle on the newly conquered lands.
Are there parallels between the announcer's comments in the video above (~1:08) about "taking control of the cow, saying 'you better do what I want'" and the description below of how celt/iberian cavalry was able to pressure and control the movement of an army?

I'm glad to see we are on the same page (I think literally in respect to the Xenophon quote, I mentioned the Herodotus sample because it is the first mention of spanish horsemen using the technique). This also ties into John Keegan's theory that the lifestyle of pastoral cultures makes them naturally suited to warfare, the opposing force being just one more herd that needs to be moved from A to B for slaughter.
There is one more thing that has to be remembered when talking about Spanish horses, is that they are also "cowy", quarter horses get this from their spanish roots. This kind of dominant behavior towards a fellow herbivore is evolutionarily seen idiotic, as such it must be a product of selective breeding. Let us take a brief look at root of what a horse being "cowy" means: a) the horse reacts to the stimulus of a third party b) it does this in order to achieve a specific goal c) when done with a rider it is done to achieve a common goal. I do not know how strong this trait is in the spanish horses in europe, but it must manifest itself in the bullfighters as a horse that couldn't read the bull wouldn't last long. I think it's also present in the south american spanish types. These are traits easily converted to warfare. They developed during spain's prehistory for the same purpose that they are used today, but in between they were also used for warfare. It was useful for the American indians for both hunting buffalo and warfare, and is therefor still very strong in surviving Spanish mustangs (not BLM). The spanish mustang basis that helped build the fundament of the quarter horse is what gives quarter horses this feature.
There are a few things that make me think this was something prized among knights the preference for spanish stock (I know I harp on about, it but it's important), the exclusive use of stallions, the dueling method of combat used can more easily exploit this than complex (and for the horse abstract) battlefield maneuvers, the love of dangerous mounted hunting activities, the long reign, and psychological aspects clear in medieval military thinking.
The preference for stallions also hinges on a couple other things, a stallion has more testosterone so he builds more muscle, a stallion is more aggressive and therefor more likely to consciously respond with a fight reaction which will naturally make him tend towards putting weight on his haunches making him naturally do rollbacks and other similar maneuvers and he's more likely to actively help you fight than a mare, we have quite a few references to warhorses fighting after the death of their riders.
A horse can understand getting closer to an enemy to strike him, a quick turn, or a swerve to avoid a rider, or turning back on a chasing enemy, or even getting into a more advantageous position. They do it all the time with each other, mine duel when they're bored. A caracole or mass pincer is more abstract and is more reliant on group training and herd dynamics.
If you want to hunt boar or bull or stag on horseback with a sword your horse needs to anticipate the movements the animal to stay safe, the riders job is to give the right angle but if the horse isn't watching the boar/bull/stag your going to have a problem anyway.
Modern "english" disciplines tend to have very tight reigns, cutting horses are ridden on short reigns. granted medieval bits were harsh enough that a horse could most likely feel very small lateral movements with the reigning hand, but having ridden with a heater shield it is very hard indeed to give many aids with the reigns at all (granted I have minimal time to work with my horse), armor also makes you want to move as little of your body as possible. Getting a horse to think with you takes just as much time as teaching one to obey your every command without thought, but in the long run I'd rather have the one I can trust to know what to do without me having to worry about my horse and my enemy at the crucial moment. The horse still needs to take your aids but he's more likely to except them if he knows what you're trying to achieve. This is I think a personal preference of the rider.
Certain facets of medieval culture make me think, that it would be the common preference. Medieval government and military at heart followed a decentralized philosophy, which caused some of the major conflicts of the medieval period, it is also what makes victorian and modern military historians yank out their hair and call the medieval military backwards. Medieval warfare consisted of the chevauchee, raids behind enemy lines by small bands. The large amount of small elite bands skilled at working independently that the feudal system produced was invaluable in reeving and raiding behind enemy lines as well as taking and holding fortified positions before defenses could be raised, but became a liability on the battlefield when it took a charismatic, respected and skilled commander to circumvent the underlying independence and take command. Getting back to the topic, it was all about Auftragsführung
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The rise of riding schools is part of the equation, this form of "cowy" horse is not as useful when doing large scale maneuvers or mounted arquebusiers, this puts different demands on horses and horsemen. The number of men that had to be mounted on well trained steeds also increased hugely. These two factors coincide with the changing of a third, the change of focus to the battlefield made warriors into officers, and created a command structure. Gone is the decentralization hello the lead up to absolutism.
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http://de.wikipedia.org/wiki/Führen_mit_Auftrag