Horses in warfare
Many cavalry units transferred in title and role to "mounted rifles": troops trained to fight on foot, but retaining mounts for rapid deployment, as well as for patrols, scouting, communications, and defensive screening. These troops differed from mounted infantry, who used horses for transport but did not perform the old cavalry roles of reconnaissance and support.

Sub-Saharan Africa: Horses were used for warfare in the central Sudan since the 9th century, where they were considered "the most precious commodity following the slave." The first conclusive evidence of horses playing a major role in the warfare of West Africa dates to the 11th century when the region was controlled by the Almoravids, a Muslim Berber dynasty. During the 13th and 14th centuries, cavalry became an important factor in the area. This coincided with the introduction of larger breeds of horse and the widespread adoption of saddles and stirrups. Increased mobility played a part in the formation of new power centers, such as the Oyo Empire in what today is Nigeria. The authority of many African Islamic states such as the Bornu Empire also rested in large part on their ability to subject neighboring peoples with cavalry. Despite harsh climate conditions, endemic diseases such as trypanosomiasis, the African horse sickness, and unsuitable terrain that limited the effectiveness of horses in many parts of Africa, horses were continuously imported and were, in some areas, a vital instrument of war. The introduction of horses also intensified existing conflicts, such as those between the Herero and Nama people in Namibia during the 19th century.
The African slave trade was closely tied to the imports of war horses, and as the prevalence of slaving decreased, fewer horses were needed for raiding. This significantly decreased the amount of mounted warfare seen in West Africa. By the time of the Scramble for Africa and the introduction of modern firearms in the 1880s, the use of horses in African warfare had lost most of its effectiveness. Nonetheless, in South Africa during the Second Boer War (1899–1902), cavalry and other mounted troops were the major combat force for the British, since the horse-mounted Boers moved too quickly for infantry to engage. The Boers presented a mobile and innovative approach to warfare, drawing on strategies that had first appeared in the American Civil War. The terrain was not well-suited to the British horses, resulting in the loss of over 300,000 animals. As the campaign wore on, losses were replaced by more durable African Basuto ponies, and Waler horses from Australia.

The Americas: The horse had been extinct in the Western Hemisphere for approximately 10,000 years prior to the arrival of Spanish Conquistadors in the early 16th century. Consequently, the Indigenous peoples of the Americas had no warfare technologies that could overcome the considerable advantage provided by European horses and gunpowder weapons. In particular this resulted in the conquest of the Aztec and Inca empires. The speed and increased impact of cavalry contributed to a number of early victories by European fighters in open terrain, though their success was limited in more mountainous regions. The Incas' well-maintained roads in the Andes enabled quick mounted raids, such as those undertaken by the Spanish while resisting the siege of Cuzco in 1536–37.
Indigenous populations of South America soon learned to use horses. In Chile, the Mapuche began using cavalry in the Arauco War in 1586. They drove the Spanish out of Araucanía at the beginning of the 17th century. Later, the Mapuche conducted mounted raids known as Malónes, first on Spanish, then on Chilean and Argentine settlements until well into the 19th century. In North America, Native Americans also quickly learned to use horses. In particular, the people of the Great Plains, such as the Comanche and the Cheyenne, became renowned horseback fighters. By the 19th century, they presented a formidable force against the United States Army.

During the American Revolutionary War (1775–1783), the Continental Army made relatively little use of cavalry, primarily relying on infantry and a few dragoon regiments. The United States Congress eventually authorized regiments specifically designated as cavalry in 1855. The newly formed American cavalry adopted tactics based on experiences fighting over vast distances during the Mexican War (1846–1848) and against indigenous peoples on the western frontier, abandoning some European traditions.
During the American Civil War (1861–1865), cavalry held the most important and respected role it would ever hold in the American military. Field artillery in the American Civil War was also highly mobile. Both horses and mules pulled the guns, though only horses were used on the battlefield. At the beginning of the war, most of the experienced cavalry officers were from the South and thus joined the Confederacy, leading to the Confederate Army's initial battlefield superiority. The tide turned at the 1863 Battle of Brandy Station, part of the Gettysburg campaign, where the Union cavalry, in the largest cavalry battle ever fought on the American continent, ended the dominance of the South. By 1865, Union cavalry were decisive in achieving victory. So important were horses to individual soldiers that the surrender terms at Appomattox allowed every Confederate cavalryman to take his horse home with him. This was because, unlike their Union counterparts, Confederate cavalrymen provided their own horses for service instead of drawing them from the government.

20th century: Although cavalry was used extensively throughout the world during the 19th century, horses became less important in warfare at the beginning of the 20th century. Light cavalry was still seen on the battlefield, but formal mounted cavalry began to be phased out for combat during and immediately after World War I, although units that included horses still had military uses well into World War II.

World War I: World War I saw great changes in the use of cavalry. The mode of warfare changed, and the use of trench warfare, barbed wire and machine guns rendered traditional cavalry almost obsolete. Tanks, introduced in 1917, began to take over the role of shock combat.
Early in the War, cavalry skirmishes were common, and horse-mounted troops widely used for reconnaissance. On the Western Front cavalry were an effective flanking force during the "Race to the Sea" in 1914, but were less useful once trench warfare was established. There a few examples of successful shock combat, and cavalry divisions also provided important mobile firepower. Cavalry played a greater role on the Eastern Front, where trench warfare was less common. On the Eastern Front, and also against the Ottomans, the "cavalry was literally indispensable." British Empire cavalry proved adaptable, since they were trained to fight both on foot and while mounted, while other European cavalry relied primarily on shock action.
On both fronts, the horse was also used as a pack animal. Because railway lines could not withstand artillery bombardments, horses carried ammunition and supplies between the railheads and the rear trenches, though the horses generally were not used in the actual trench zone. This role of horses was critical, and thus horse fodder was the single largest commodity shipped to the front by some countries. Following the war, many cavalry regiments were converted to mechanised, armoured divisions, with light tanks developed to perform many of the cavalry's original roles.

World War II: Several nations used horse units during World War II. The Polish army used mounted infantry to defend against the armies of Nazi Germany during the 1939 invasion. Both the Germans and the Soviet Union maintained cavalry units throughout the war, particularly on the Eastern Front. The British Army used horses early in the war, and the final British cavalry charge was on March 21, 1942, when the Burma Frontier Force encountered Japanese infantry in central Burma. The only American cavalry unit during World War II was the 26th Cavalry. They challenged the Japanese invaders of Luzon, holding off armoured and infantry regiments during the invasion of the Philippines, repelled a unit of tanks in Binalonan, and successfully held ground for the Allied armies' retreat to Bataan.
Throughout the war, horses and mules were an essential form of transport, especially by the British in the rough terrain of Southern Europe and the Middle East. The United States Army utilised a few cavalry and supply units during the war, but there were concerns that the Americans did not use horses often enough. In the campaigns in North Africa, generals such as George S. Patton lamented their lack, saying, "had we possessed an American cavalry division with pack artillery in Tunisia and in Sicily, not a German would have escaped."
The German and the Soviet armies used horses until the end of the war for transportation of troops and supplies. The German Army, strapped for motorised transport because its factories were needed to produce tanks and aircraft, used around 2.75 million horses – more than it had used in World War I. One German infantry division in Normandy in 1944 had 5,000 horses. The Soviets used 3.5 million horses.

Recognition: While many statues and memorials have been erected to human heroes of war, often shown with horses, a few have also been created specifically to honor horses or animals in general. One example is the Horse Memorial in Port Elizabeth in the Eastern Cape province of South Africa. Both horses and mules are honored in the Animals in War Memorial in London's Hyde Park.
Horses have also at times received medals for extraordinary deeds.