Horses in warfare
Harness and vehicles: The invention of the wheel was a major technological innovation that gave rise to chariot warfare. At first, equines, both horses and onagers, were hitched to wheeled carts by means of a yoke around their necks in a manner similar to that of oxen. However, such a design is incompatible with equine anatomy, limiting both the strength and mobility of the animal. By the time of the Hyksos invasions of Egypt, c. 1600 BC, horses were pulling chariots with an improved harness design that made use of a breastcollar and breeching, which allowed a horse to move faster and pull more weight.
Even after the chariot had become obsolete as a tool of war, there still was a need for technological innovations in pulling technologies; horses were needed to pull heavy loads of supplies and weapons. The invention of the horse collar in China during the 5th century AD (Northern and Southern dynasties) allowed horses to pull greater weight than they could when hitched to a vehicle with the ox yokes or breast collars used in earlier times. The horse collar arrived in Europe during the 9th century, and became widespread by the 12th century.

Riding equipment: Two major innovations that revolutionised the effectiveness of mounted warriors in battle were the saddle and the stirrup. Riders quickly learned to pad their horse's backs to protect themselves from the horse's spine and withers, and fought on horseback for centuries with little more than a blanket or pad on the horse's back and a rudimentary bridle. To help distribute the rider's weight and protect the horse's back, some cultures created stuffed padding that resembles the panels of today's English saddle. Both the Scythians and Assyrians used pads with added felt attached with a surcingle or girth around the horse's barrel for increased security and comfort. Xenophon mentioned the use of a padded cloth on cavalry mounts as early as the 4th century BC.
The saddle with a solid framework, or "tree", provided a bearing surface to protect the horse from the weight of the rider, but was not widespread until the 2nd century AD. However, it made a critical difference, as horses could carry more weight when distributed across a solid saddle tree. A solid tree, the predecessor of today's Western saddle, also allowed a more built-up seat to give the rider greater security in the saddle. The Romans are credited with the invention of the solid-treed saddle.
An invention that made cavalry particularly effective was the stirrup. A toe loop that held the big toe was used in India possibly as early as 500 BC, and later a single stirrup was used as a mounting aid. The first set of paired stirrups appeared in China about 322 AD during the Jin dynasty. Following the invention of paired stirrups, which allowed a rider greater leverage with weapons, as well as both increased stability and mobility while mounted, nomadic groups such as the Mongols adopted this technology and developed a decisive military advantage. By the 7th century, due primarily to invaders from Central Asia, stirrup technology spread from Asia to Europe. The Avar invaders are viewed as primarily responsible for spreading the use of the stirrup into central Europe. However, while stirrups were known in Europe in the 8th century, pictorial and literary references to their use date only from the 9th century. Widespread use in Northern Europe, including England, is credited to the Vikings, who spread the stirrup in the 9th and 10th centuries to those areas.

Tactics: The first archaeological evidence of horses used in warfare dates from between 4000 and 3000 BC in the steppes of Eurasia, in what today is Ukraine, Hungary, and Romania. Not long after domestication of the horse, people in these locations began to live together in large fortified towns for protection from the threat of horseback-riding raiders, who could attack and escape faster than people of more sedentary cultures could follow. Horse-mounted nomads of the steppe and current day Eastern Europe spread Indo-European Languages as they conquered other tribes and groups.
The use of horses in organised warfare was documented early in recorded history. One of the first depictions is the "war panel" of the Standard of Ur, in Sumer, dated c. 2500 BC, showing horses (or possibly onagers or mules) pulling a four-wheeled wagon.

Chariot warfare: Among the earliest evidence of chariot use are the burials of horse and chariot remains by the Andronovo (Sintashta-Petrovka) culture in modern Russia and Kazakhstan, dated to approximately 2000 BC. The oldest documentary evidence of what was probably chariot warfare in the Ancient Near East is the Old Hittite Anitta text, of the 18th century BC, which mentioned 40 teams of horses at the siege of Salatiwara. The Hittites became well known throughout the ancient world for their prowess with the chariot. Widespread use of the chariot in warfare across most of Eurasia coincides approximately with the development of the composite bow, known from c. 1600 BC. Further improvements in wheels and axles, as well as innovations in weaponry, soon resulted in chariots being driven in battle by Bronze Age societies from China to Egypt.
The Hyksos invaders brought the chariot to Ancient Egypt in the 16th century BC and the Egyptians adopted its use from that time forward. The oldest preserved text related to the handling of war horses in the ancient world is the Hittite manual of Kikkuli, which dates to about 1350 BC, and describes the conditioning of chariot horses.
Chariots existed in the Minoan civilization, as they were inventoried on storage lists from Knossos in Crete, dating to around 1450 BC. Chariots were also used in China as far back as the Shang dynasty (c. 1600–1050 BC), where they appear in burials. The high point of chariot use in China was in the Spring and Autumn period (770–476 BC), although they continued in use up until the 2nd century BC.
Descriptions of the tactical role of chariots in Ancient Greece and Rome are rare. The Iliad, possibly referring to Mycenaen practices used c. 1250 BC, describes the use of chariots for transporting warriors to and from battle, rather than for actual fighting. Later, Julius Caesar, invading Britain in 55 and 54 BC, noted British charioteers throwing javelins, then leaving their chariots to fight on foot.

Cavalry: Some of the earliest examples of horses being ridden in warfare were horse-mounted archers or javelin-throwers, dating to the reigns of the Assyrian rulers Ashurnasirpal II and Shalmaneser III. However, these riders sat far back on their horses, a precarious position for moving quickly, and the horses were held by a handler on the ground, keeping the archer free to use the bow. Thus, these archers were more a type of mounted infantry than true cavalry. The Assyrians developed cavalry in response to invasions by nomadic people from the north, such as the Cimmerians, who entered Asia Minor in the 8th century BC and took over parts of Urartu during the reign of Sargon II, approximately 721 BC. Mounted warriors such as the Scythians also had an influence on the region in the 7th century BC. By the reign of Ashurbanipal in 669 BC, the Assyrians had learned to sit forward on their horses in the classic riding position still seen today and could be said to be true light cavalry. The ancient Greeks used both light horse scouts and heavy cavalry, although not extensively, possibly due to the cost of keeping horses.
Heavy cavalry was believed to have been developed by the Ancient Persians, although others argue for the Sarmatians. By the time of Darius (558–486 BC), Persian military tactics required horses and riders that were completely armoured, and selectively bred a heavier, more muscled horse to carry the additional weight. The cataphract was a type of heavily armoured cavalry with distinct tactics, armour, and weaponry used from the time of the Persians up until the Middle Ages.
In Ancient Greece, Phillip of Macedon is credited with developing tactics allowing massed cavalry charges. The most famous Greek heavy cavalry units were the companion cavalry of Alexander the Great. The Chinese of the 4th century BC during the Warring States period (403–221 BC) began to use cavalry against rival states. 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.