Ah, the Cavalry Charge something that's fun to read about and fun to watch and fun to write or write about . . . And something that's the Holy Grail of Bones of Contention for Military Historians everywhere - Not many people can butcher a phrase the way I can ;P - Military Historians such as John Keegan say that horses can't charge what they think is a solid object, i.e Solid Infantry. Keegan bases his theory on Agincourt and Waterloo.
At Agincourt Jean Froissart mentions one incident where some French Heavy Cavalry crashed through a hedge. At Waterloo the French Cavalry were not as good as they had been, earlier in the war at Eylau some of Napoleons Lancers hacked their way through the front of a block of solid Russian Infantry and even later at Omdurman the 21st Lancers charged home and broke solid infantry. Those are just a few examples, so lets say you have cavalry in your book. Okay, that's cool. Where did the Cavalry come from? Where did your nation procure the gear and the mounts? Horses cost money, Warhorses cost even more (One chronicle records one Warhorse as having the same price as twelve good oxen) and when you add things like remounts and people to care for the horse . . . Where are you gonna keep these horses? A Stable will also need Corrals and Pastures and Paddocks and Training grounds for a Warhorse as well as a ready supply of water and food - 30 horses can eat the grass of large pasture down to the dirt in a few weeks - and when the rain comes and there's no grass and you have 30 1,500 pound Horses walking around you get mud, very deep mud as it happens. Where are your people? You will need vets, you will need Trainers, you will need Grooms. Vets keep your horses in good health and are very helpful when it comes time for the Foal to be born. Trainers get the Horses broken in and trained in the things that they and their rider will need to know. Grooms keep your horses clean and fed and watered, they muck out stalls, they maintain tack, they rub the horses down. Horses digest food so there's another reason why you need Grooms and then the Manure can be spread out over the pasture where the grass that the Horses ate down to the dirt, thus bringing back the Grass and then said Grass can be used to feed the horses and you can make Hay from it thus easing some of the strain of keeping those Horses fed. You will also need Farriers and Builders. Farriers keep your Horses shod and keep the hooves healthy. Builders build new stalls and fences and repair existing buildings. You might also wanna consider Peasants, they can cultivate land for the Horses, divert water, etc. Then you have to have resources for things like wood and leather for saddles and buildings and then someone to make a saddle from the raw materials and then you have to have an Armourer. Then you get to the rider, he has to have lots of training and then you can pair the horse(s) and the rider. Do the cavalry even ride Horses? If not you had better consider all the aspects written above. Consider the Horses physiology, a Destrier is around 15-16 hands tall and has a short arched neck, strong thick hindquarters, a convex head, a short strong back and powerful legs as well as thick chest, they were extremely agile and they were Stallions and as such extremely aggressive, they were trained to bite, kick, and target people and are mentioned ripping peoples faces off and carrying off people in their teeth however until Barding became widespread Destriers were generally used in tournaments because of their expense 'Knights' generally used Coursers and Rouncey's a Courser was as tall as a Destrier and of a lighter build they were also favored for Hunting. A Rouncey was again about as tall but they were more a 'jack-of-all-trades' type then their counterparts. Note: These Horses weren't breeds they were a class. So once you have the cost and the facility figured out and the rider and the gear and tack you now have to decide what you're going to use the Cavalry for and what type they are. Are they going to be Light Cavalry? If so Light Horse is fairly cheap (considering) and you can use them for Scouting, Recon, Foraging, Exploitation, Ambush, Harrassment and Pursuit and you can pile them on the enemy's flanks and rear and you can use them to menace the enemy's flanks and rear so they keep turning to face you and then pound them with something they're stationary. You can use them as bait and for feinting attacks, you can use them to sweep their enemy counterparts off the field, you can use them for deep raids into enemy territory to wreak havoc, you can use them to add more pushing power to the Heavy Horse. They will have at least some type of protection and will be armed with missile weapons as well as a hand weapon. Medium Cavalry can be used for the same things as Light cavalry and it's somewhat hard to distingush between the two, generally medium horse are better protected and have a better shock value. Heavy Horse are the Iron Fist of your Army, their riders will have lots of protection and be more heavily armed and it's best to armour the horses as well they will have a shock weapon and won't usually carry missile weapons. While they can be used to exploit gaps and flank attacks, Light and Medium Horse can do that just as well, Heavy Horse should be used to sweep the enemy Horse from the field or as the sucker punch or to knock holes in the enemy lines while medium horse and heavy infantry follow up the Heavy Cavalry's attack. You can also use them as bait and as a feint and to menace the enemy flanks and to screen lighter armed troops from the enemy. Because they can't usually (Unless they're Husaria derivatives) perform the strategic roles of Light and Medium Cavalry they're a tactical weapon. Heavy Horse would have at least one remount in the case of the Burgundian and French Gendarmes (And presumably cavalrymen as heavily equipped as they were!) three was the minimum with five being the preferred number. The Polish Husaria also had several remounts hence the mobility and speed they were noted for. Presumably if you had time the cavalrymen would trained to fight on foot on as well.