Alexander the Great had Bucephalus, Napoleon had Marengo, the Duke of Wellington had Copenhagen. For centuries and across continents, horses were the most ubiquitous animals in warfare, essential to nomadic warriors and established militaries alike. They carried the feared Huns to Europe, drew the chariots of the Romans and crusaded in the Middle Ages. (What's a knight without a noble steed?) They participated in revolutions, and took bullets in World War I. Technological advances led to their widespread retreat from the front lines, but horses are still used today, mainly by militias like the Janjaweed in Sudan.