Horses in warfare
To fight nomadic raiders from the north and west, the Chinese of the Han dynasty (202 BC – 220 AD) developed effective mounted units. Cavalry was not used extensively by the Romans during the Roman Republic period, but by the time of the Roman Empire, they made use of heavy cavalry. However, the backbone of the Roman army was the infantry.

Horse artillery: Once gunpowder was invented, another major use of horses was as draught animals for heavy artillery, or cannon. In addition to field artillery, where horse-drawn guns were attended by gunners on foot, many armies had artillery batteries where each gunner was provided with a mount. Horse artillery units generally used lighter pieces, pulled by six horses. "9-pounders" were pulled by eight horses, and heavier artillery pieces needed a team of twelve. With the individual riding horses required for officers, surgeons and other support staff, as well as those pulling the artillery guns and supply wagons, an artillery battery of six guns could require 160 to 200 horses. Horse artillery usually came under the command of cavalry divisions, but in some battles, such as Waterloo, the horse artillery were used as a rapid response force, repulsing attacks and assisting the infantry. Agility was important; the ideal artillery horse was 1.5 to 1.6 metres (15 to 16 hands) high, strongly built, but able to move quickly.

Asia: 

Central Asia: Relations between steppe nomads and the settled people in and around Central Asia were often marked by conflict. The nomadic lifestyle was well suited to warfare, and steppe cavalry became some of the most militarily potent forces in the world, only limited by nomads' frequent lack of internal unity. Periodically, strong leaders would organise several tribes into one force, creating an almost unstoppable power. These unified groups included the Huns, who invaded Europe, and under Attila, conducted campaigns in both eastern France and northern Italy, over 500 miles apart, within two successive campaign seasons. Other unified nomadic forces included the Wu Hu rebellions in China, and the Mongol conquest of much of Eurasia.

South Asia: The literature of ancient India describes numerous horse nomads. Some of the earliest references to the use of horses in South Asian warfare are Puranic texts, which refer to an attempted invasion of India by the joint cavalry forces of the Sakas, Kambojas, Yavanas, Pahlavas, and Paradas, called the "five hordes" (pañca.ganah) or "Kśatriya" hordes (Kśatriya ganah). About 1600 BC, they captured the throne of Ayodhya by dethroning the Vedic king, Bahu. Later texts, such as the Mahābhārata, c. 950 BC, appear to recognise efforts taken to breed war horses and develop trained mounted warriors, stating that the horses of the Sindhu and Kamboja regions were of the finest quality, and the Kambojas, Gandharas, and Yavanas were expert in fighting from horses.
In technological innovation, the early toe loop stirrup is credited to the cultures of India, and may have been in use as early as 500 BC. Not long after, the cultures of Mesopotamia and Ancient Greece clashed with those of central Asia and India. Herodotus (484–425 BC) wrote that Gandarian mercenaries of the Achaemenid Empire were recruited into the army of emperor Xerxes I of Persia (486–465 BC), which he led against the Greeks. A century later, the "Men of the Mountain Land," from north of Kabul River, served in the army of Darius III of Persia when he fought against Alexander the Great at Arbela in 331 BC. In battle against Alexander at Massaga in 326 BC, the Assakenoi forces included 20,000 cavalry. The Mudra-Rakshasa recounted how cavalry of the Shakas, Yavanas, Kambojas, Kiratas, Parasikas, and Bahlikas helped Chandragupta Maurya (c. 320–298 BC) defeat the ruler of Magadha and take the throne, thus laying the foundations of Mauryan dynasty in Northern India.
Mughal cavalry used gunpowder weapons, but were slow to replace the traditional composite bow. Under the impact of European military successes in India, some Indian rulers adopted the European system of massed cavalry charges, although others did not. By the 18th century, Indian armies continued to field cavalry, but mainly of the heavy variety.

East Asia: The Chinese used chariots for horse-based warfare until light cavalry forces became common during the Warring States era (402–221 BC). A major proponent of the change to riding horses from chariots was Wu Ling, c. 320 BC. However, conservative forces in China often opposed change, as cavalry did not benefit from the additional cachet attached to being the military branch dominated by the nobility as in medieval Europe. Nevertheless, during the reign of Emperor Wu of Han (r. 141–87 BC), it is recorded that 300,000 government-owned horses were insufficient for the cavalry and baggage trains of the Han military in the campaigns to expel the Xiongnu nomads from the Ordos Desert, Qilian Mountains, Khangai Mountains and Gobi Desert, spurring new policies that encouraged households to hand over privately-bred horses in exchange for military and corvee labor exemptions.
The Japanese samurai fought as cavalry for many centuries. They were particularly skilled in the art of using archery from horseback. The archery skills of mounted samurai were developed by training such as Yabusame, which originated in 530 AD and reached its peak under Minamoto no Yoritomo (1147–1199 AD) in the Kamakura period. They switched from an emphasis on mounted bowmen to mounted spearmen during the Sengoku period (1467–1615 AD).

Middle East: During the period when various Islamic empires controlled much of the Middle East as well as parts of West Africa and the Iberian peninsula, Muslim armies consisted mostly of cavalry, made up of fighters from various local groups, mercenaries and Turkoman tribesmen. The latter were considered particularly skilled as both lancers and archers from horseback. In the 9th century the use of Mamluks, slaves raised to be soldiers for various Muslim rulers, became increasingly common. Mobile tactics, advanced breeding of horses, and detailed training manuals made Mamluk cavalry a highly efficient fighting force. The use of armies consisting mostly of cavalry continued among the Turkish people who founded the Ottoman Empire. Their need for large mounted forces led to an establishment of the sipahi, cavalry soldiers who were granted lands in exchange for providing military service in times of war.
Mounted Muslim warriors conquered North Africa and the Iberian Peninsula during the 7th and 8th centuries AD following the Hijrah, of Muhammad in 622 AD. By 630 AD, their influence expanded across the Middle East and into western North Africa. By 711 AD, the light cavalry of Muslim warriors had reached Spain, and controlled most of the Iberian peninsula by 720. Their mounts were of various oriental types, including the North African Barb. A few Arabian horses may have come with the Ummayads who settled in the Guadalquivir valley. Another strain of horse that came with Islamic invaders was the Turkoman horse. Muslim invaders travelled north from present-day Spain into France, where they were defeated by the Frankish ruler Charles Martel at the Battle of Tours in 732 AD.

Europe: 

Antiquity: 

Middle Ages: During the European Middle Ages, there were three primary types of war horses: the destrier, the courser, and the rouncey, which differed in size and usage. A generic word used to describe medieval war horses was charger, which appears interchangeable with the other terms. The medieval war horse was of moderate size, rarely exceeding 15.2 hands (62 inches, 157 cm). Heavy horses were logistically difficult to maintain and less adaptable to varied terrains. The destrier of the early Middle Ages was moderately larger than the courser or rouncey, in part to accommodate heavier armoured knights. However, destriers were not as large as draught horses, averaging between 14.2 hands (58 inches, 147 cm) and 15 hands (60 inches, 152 cm). On the European continent, the need to carry more armour against mounted enemies such as the Lombards and Frisians led to the Franks developing heavier, bigger horses. As the amount of armour and equipment increased in the later Middle Ages, the height of the horses increased; some late medieval horse skeletons were of horses over 1.5 metres (15 hands).
Stallions were often used as destriers due to their natural aggression. However, there may have been some use of mares by European warriors, and mares, who were quieter and less likely to call out and betray their position to the enemy, were the preferred war horse of the Moors, who invaded various parts of Southern Europe from 700 AD through the 15th century. Geldings were used in war by the Teutonic Knights, and known as "monk horses" (German: Mönchpferde or Mönchhengste).