The example of the fencing masters is quite apt. When skills of those of the past are lost it's normal for those of the present to denigrate people of the past and hold their own superior. After all, don't things improve over time? Progress is progress after all. True verbal commands are hard on a battlefield, but they are how it was done and still is in most cases at the squad level (believe me I know). As a Civil War reenactor whose done cavalry (and Civil War battlefields were much louder than Medieval ones to be sure) I could command my horse with voice commands (how I made him halt with a pistol in one hand and the shotgun in the other) despite gunshots, shouts, cannon and thundering hooves (thats what they really sound like!). True, I prefered knees, but thats mainly for steering, not giving complex commands, for these you need voice commands (you'll notice that nearly all physical commands are accompanied by voice commands as well). Plus a horse is nearly as smart as a dog, and if a dog can do it.
You can follow voice commands despite the noise once you know your leader's voice. It's kind of like (a loose anology here) hearing and listening to a single voice across a noisy, crowded room.
I did in fact mention several instances of horses defending and attacking while Lipps did in fact "do there thing" on the battlefield (well documented). Cavalry manuals dating as far back as those written by the Greeks give direction on breeding and training as do cavalry manuals of the 19th century. In some cases then, horses were better trained than the riders! Most Medieval and Rennaissance manuals are not in print though manuscripts do exist.
King, you are quite right about CATTLE, they are DUMB. Having worked around them, I have VERY low opinion of a bull's brain power. They are aggressive, but far from bright. To compare cattle to horses however, is like comparing apples and oranges. Yes they are both large grazers, but horses are a whole level above, nearly dog-like (they HAVE been bred to be partners and thus for intelligence for millenia). Cattle have been bred for food, labor, or for ferocity and definitely not their brains. Did I mention they are dumb?
Lets be clear on thing here above all else: these animals were and are similar to todays rescue, war, and police dogs. In other words the elite and a small elite to boot. The vast number of horse were simple riding beasts no different form today's riding horses. Not mention I did point out even amongst war horses the quality of training discussed was uncommon, the bulk taught only a few commands needed. The fully trained variety were as expensive as a modern M1 Abrams battle tanks(how many you think can afford one of their very own?). Now add in cost of armor, weaponry, upkeep (horses are freakin expensive to keep up!). Add in the years needed to train and you get the idea of how rare they are.
I know it's hard to believe what I've pointed out but my own personal experience says it's possible. Research such as that done by Lipp breeders and the Royal Armoury Museum in Leeds (Britain) says it as well.