Deleuze and Guattari mention the stirrup as a pivotal invention that helped Genghis Khan to conquer a great part of the world. With the aid of the stirrup, horsemen became man-horse-lance assemblages. This is another way of talking about structural coupling.
The lance and the sword came into being in the Bronze Age only by virtue of the man-horse assemblage, which caused a lengthening of the dagger and pike, and made the first infantry weapons, the morning star and the battle-ax, obsolete. The stirrup, in turn, occasioned a new figure of the man-horse assemblage, entailing a new type of lance and new weapons, and has different conditions depending on whether it is bound up with the general conditions of nomadism, or later readapted to the sedentary conditions of feudalism.A Thousand Plateaus, p. 399
The stirrup allowed the rider to stand up, use the leverage of the stirrup to gain trusting power, and twist around and shoot arrows while retreating. The Cossacks , who have played an important role in Russia’s wars since the 18th century, belong to this ancient tradition of warrior horsemen.
But what is the point of analyzing things like stirrups? Assemblage theory might seem kind of trivial. The point, though, is to revise the old view of the autonomous, independent subject—the kind of assumption behind statements like “The Aztecs and Incas lost because they were bad fighters.”
The following is from Encyclopedia of Society and Culture in the Medieval World:.
The nomadic way of life was so different from that of settled agricultural civilizations like China and western Europe that, once he had conquered northern China, the Mongol ruler
Genghis Khan considered massacring the entire population of farmers because he could not imagine what use they served in society. Trained by their way of life on the steppe, the populations of inner Asia produced the finest cavalrymen in the world. The steppe tribes usually had little trouble attacking and overcoming more settled populations when they wished. The Great Wall of China was built and maintained as a not entirely successful means of containing them. Iranian horsemen from inner Asia in the first millennium b.c.e. had conquered the Near East and southern Russia and occasionally raided China. But the stirrup was developed in this area during the early Middle Ages, making nomadic life on horseback much easier and cavalrymen still more effective as soldiers. Thereafter, migrations of peoples from this area, such as the Huns, Magyars and Turks, led to the collapse of the western Roman Empire, the general collapse of civilization in western
Europe known as the Viking Age (850–1500), the collapse of the Byzantine Empire (1453), and the conquest of much of eastern Europe by the Turks. . . .
To the east of the Caspian Sea and the north of the Plateau of Iran lie the inner Asian steppes. This vast area of grassland supported many peoples who lived from horse breeding and who consequently made highly effective cavalry and were repeatedly able to successfully raid and conquer more settled peoples in Europe, India, and China. The stirrup, which makes riding and especially fighting from a horse much easier, was invented in this area at the very beginning of the Middle Ages. To some degree this development triggered an outward migration from inner Asia that eventually overwhelmed the Roman Empire.Encyclopedia of Society and Culture in the Medieval World, Volumes 1-4, edited by Pam J. Crabtree, Facts On File, Incorporated, 2008. ProQuest Ebook Central, https://ebookcentral.proquest.com/lib/nu/detail.action?docID=3009931.
The invention of the rifle, as Foucault mentions, had a similar effect on warfare. The saddle was, of course, also very important for military horsemen. From a journal article on the history of the saddle:
Horse ammunition was formed historically on a large geographical area. The mostLukyashko, S. (2019). Horse Ammunition. From the History of a Saddle. Vestnik Volgogradskogo Gosudarstvennogo Universiteta. Serii͡a︡ 4, Istorii͡a, 5, 6–18. https://doi.org/10.15688/jvolsu4.2019.5.1
important component of it is a saddle. The ancient history of a saddle is not sufficiently investigated. It should be safely assumed that the oldest forms of seats appear together with the use of a horse for riding. We can confidently say that the appearance of the horsemen of the Cimmerians and Scythians in Western Asia in 8th – 7th centuries BC would not have been possible if there had been no such devices. There is a deep belief that horse riding in Western Asia arose under the Cimmerian-Scythian influence. . . . The archaeological material clearly indicates that a saddle was formed within the culture of Eurasian nomads in the 1st millennium BC, a rigid saddle appeared in the Scythian
culture in the late 4th century BC.