In the Middle Ages, a destrier was a superior war horse, selected for strength and a calm nature to be trained for the battlefield. Along with rounceys and coursers, two other types of medieval battlefield horses, it was classified as a charger. However, the destrier was considered to be the highest quality of battle horse, fetching a high price and being ridden by upper ranking knights only. Many of the horses depicted in medieval artwork are destriers.
The name derives from the Latin dexter, meaning right side or right handed. This is because the horses were only ridden in battle; while traveling, a destrier would have been led at the knight's right side until it was needed. The name is also descriptive of a type of horse, rather than a specific breed, and study of art and writing from the period in which destriers were used suggests that they were of an average height and extremely muscular build. It is likely that Iberian horses such as the Andalusian were used to breed destriers, as they have a reputation for immense physical strength, agility, and a calm nature, which is vital in a chaotic battlefield.
This is all in opposition to beliefs held by researchers over much of the twentieth century, which had held that the destrier was an immense horse similar in build to the modern draft horse. While draft horses were probably cross bred with other horses for use as destriers, they did not have the maneuverability of lighter horse breeds which would have been vitally necessary on the battlefield. Above all, a destrier had to be loyal and brave, and these traits were sought out in young horses being considered for training.
The destrier was selected for brute strength, but not endurance. In addition to carrying an armored knight, the horse was also armored, meaning that it had a great deal of weight to carry. In a short encounter such as a clash on the battlefield, the destrier's strength could carry the weight, but it was not capable of maintaining a high level of physical work. Some destriers were also trained to fight alongside their riders, mainly by rearing and attacking fighters on foot.
Knights who were able to afford a destrier typically kept several coursers as well. Coursers closely resemble the modern hunter, and were used for speed and agility. They also had more stamina than destriers, and were a good deal less costly. An ordinary horse, known as a rouncey, would be used by squires and low ranking knights. For pleasure riding, knights would typically use a palfrey, or riding horse.