The Domestication of the Horse, and Everything That Unleashed
There have been many historic events that have resulted in quantum leaps in the business of warfare, and without doubt the domestication of the horse was one these. The domestication of animals in general was a seminal moment in human history, almost as important as the control and use of fire. It revolutionized transport, husbandry and agriculture, but most importantly, it revolutionized warfare. The horse remained part of the business of organized warfare until the advent of WWI, and in fact millions of horses were introduced into the European theatre from every part of the world during that vast conflagration.
The great age of the horse in warfare, however, began over 5,000 years ago, and the first evidence of the use of horses on the battlefield exists in a Sumerian illustration dating to 2500 BCE, which depicts a horse pulling a wagon in a war setting. The use of draft animals, including horses, in warfare dates back, one might suppose, to the dawn of equine domestication, but the first use of horses in combat came with the development of chariots as an attack weapon and fire platform. This was made possible, of course, thanks to advances in chariot design, but also in the progressive, selective breeding of horses to create a beast compatible with a chariot, and then the development of harnesses and tactics of horsemanship.
The next major advance came with the advent of modern styles of saddle, and most importantly, the stirrup. The stirrup made it possible for the rider to be less preoccupied with staying on the horse and more with the deployment of his hands and body for the purpose of combat.
As tactics of warfare developed, so too did the diversification of horses bred for specific functions. The most humble tasks of hauling and carrying often fell to the donkey or the mule, an ever-present member of any organized army, and horses varied widely depending on their task. Horses provided the mobility that served the nomadic hordes of Central Asia, and certainly the Mongol Invasions would never have been possible without horses suited to light cavalry. The heavy armored cavalry of the Middle Ages demanded commensurately heavy horses, and the battle horses of the age where bred for weight and strength rather than agility.
The age of the armored knight came to an end with the advent of gunpowder, and the emphasis once again shifted to light cavalry. In combination with the advanced infantry tactic of the Napoleonic era, light cavalry was often a crucial component of victory. Later, in Anglo Boer War and the Indian Wars of the early United States, horses played a crucial role in battlefield reconnaissance and in the development of early guerrilla warfare.
The use of horses in warfare came to an end during WWI, and if fact, during that war, horses were largely returned to a support role, their usefulness in combat diminished entirely by the development of the machine gun. Today horses remain in the ranks, but only really in a ceremonial role.