Warhorses and the Eastern Provinces: A Summary Note on Political History and Horses

Himiko and the Records of the Three Kingdoms (Wajinden)
The following description is found in the Account of the Wa in the Wei Zhi (Records of the Three Kingdoms, Book of Wei, Eastern Barbarians section):

「其地無牛馬虎豹羊鵲」
(That land has no oxen, horses, tigers, leopards, sheep, or magpies.)

When envoys from Wei visited Japan, it was perceived by the Chinese side that "neither horses nor oxen existed" in the countries of the Yamatai confederation at that time (the era of Himiko; presumed to be the Yamato administration under the Sujin dynasty).
While horse bones are occasionally found in Jomon and Yayoi period ruins (such as shell mounds), it has been determined that almost all of these are intrusions from the Kofun period or later.
It is considered that horses were systematically introduced to the Japanese archipelago and used as livestock from the mid-Kofun period onwards, specifically from the late 4th to 5th century, about 150 to 200 years after the era of Himiko, when immigrants from the Korean Peninsula transmitted horse-rearing techniques.

The Ojin Dynasty (Kawachi Dynasty)
The process by which horses, which did not exist in the era of Himiko, were introduced to the Japanese archipelago between the late 4th and 5th centuries (mid-Kofun period) is deeply linked to the intense warfare in East Asia at that time.
East Asia in the 4th century was in a period of great upheaval known as the Sixteen Kingdoms of the Five Barbarians. During this period, the tactics of heavy cavalry (powerful cavalry where both men and horses wore armor), which had developed in northern China, were transmitted to the Korean Peninsula. In the late 4th century, the Wa state, having formed alliances with Baekje and the Gaya confederacy in the southern Korean Peninsula for the sake of iron resource interests, advanced into the peninsula. Around 400 AD, the Wa army clashed with a cavalry corps led by King Gwanggaeto the Great of Goguryeo in northern Korea and suffered a crushing defeat (Gwanggaeto Stele). The Yamato administration, which was centered on infantry, was shocked by the overwhelming strength of cavalry tactics. To counter Goguryeo and acquire cutting-edge military power, they launched a national-scale project to import horses and horse-rearing technicians (especially immigrants from Baekje and Gaya) as a set to the Japanese archipelago. The Yamato administration organized these groups of technicians into a professional group called the Umakaibe (also known as Umakaibe).
Horses and immigrants settled at the foot of Mount Ikoma and around the Kawachi Lake in Kawachi Province, which was blessed with water, grass, and undulating terrain, forming the "Kawachi Umakai," the first horse-rearing group in Japan.
From the Shitomiyakita ruins in Shijonawate City, Osaka Prefecture, the almost complete skeleton of a 5th-century horse, stakes used to tether horses, and a large quantity of Korean-style pottery (Hanseiki doki) used by the immigrants were unearthed. It can be called the first horse-rearing and research center in the Japanese archipelago.
The horse-rearing and breeding techniques established in Kawachi in the 5th century were transplanted and expanded into the Kanto region (such as Kamitsukeno) and the Tosando region (Shinano and Kai), where vast, high-quality grasslands spread, as the 6th century began.

King Bu of Wa (Emperor Yuryaku)
The memorial sent by King Bu of Wa (great-grandson of Ojin, Emperor Yuryaku) to the Emperor of China (Song) in 478 AD (Book of Song, Account of Wa) chronicles a history of tremendous wars of conquest spanning generations.

「昔より祖禰（そね）、躬（みずか）ら甲冑を擐（つらぬ）き、山川を跋渉（ばっしょう）し、寧処（ねい処）に遑（いとま）あらず。東は毛人を征すること五十五国、西は衆夷を服すること六十六国、渡りて海北を平ぐること九十五国……」
(Since ancient times, my ancestors have personally donned armor, crossed mountains and rivers, and fought without rest. We conquered 55 countries of the hairy people in the east, subjugated 66 countries of various barbarians in the west, and crossed the sea to pacify 95 countries in the north (southern Korean Peninsula)...)

From the kofun (tumuli) of the era of Emperor Yuryaku (late 5th century), a massive and luxurious amount of iron weapons and horse trappings (bits, saddles, stirrups, etc.) have been unearthed, incomparable to previous eras. From this period onwards, glittering gilt-bronze horse trappings and large quantities of haniwa (terracotta figures) of horses began to be found in the kofun of powerful local clans (such as in Kamitsukeno and Shinano).

The Jinshin War: Prince Oama's Coup and the Eastern Provinces
The Jinshin War (672 AD) was the largest war of imperial succession in ancient Japanese history, occurring after the death of Emperor Tenji. Prince Oama (later Emperor Tenmu), the younger brother of Emperor Tenji, and Prince Otomo, the son of Emperor Tenji, split the country and clashed, with Prince Oama achieving a comeback victory in a lightning war lasting only about one month.
Prince Oama, who had lost his position in the Omi court and was living in seclusion in Yoshino, received word that the Omi court (the Otomo side) was plotting his assassination and escaped Yoshino with a small force. Oama headed to his private estate, the Yunomura (bath-bathing village) in Mino Province (Gifu Prefecture), via Iga and Ise, and immediately blockaded the "Fuwa no Michi" (Fuwa Road), the most important strategic point connecting the eastern and western provinces. This area corresponds to the same area as the later Battle of Sekigahara. By controlling Fuwa, he cut off the route for the Omi court to conscript soldiers from the eastern provinces, and conversely, Oama succeeded in organizing a powerful army of tens of thousands in an instant by winning over powerful clans in Mino and Owari. In particular, powerful military forces joined one after another from the Tosando (the current Koshin region), which was directly connected to the Fuwa headquarters in Mino, forming the main body of the army. The clans of Shinano and Kai were military groups skilled in horse breeding and cavalry tactics. After his accession, Emperor Tenmu highly valued the clans of Shinano and Kai who had supported him at the risk of their lives. He had many sons of Shinano clans serve as close attendants (toneri) to the Emperor, guaranteeing their status at the center. In his later years, Emperor Tenmu sent provincial governors to Shinano Province to investigate it as a candidate site for a secondary capital (the Shinano capital relocation plan. The temporary palace (kari-miya) that Tenmu had built in conjunction with the capital relocation (secondary capital) plan is called the "Tsukama no Angu." Based on the description in the Nihon Shoki that he "intended to visit the hot springs of Tsukama," it is presumed to be the current Asama Onsen in Matsumoto City, Nagano Prefecture, or the Mine-no-hara Onsen (Yamabe Onsen) in the same city). Although it was never realized, it is decisive evidence of how much importance Tenmu placed on Shinano.
The Kanasashi no Toneri clan was the largest powerful clan in Shinano, possessing a powerful network of clans from the current Suwa region of Nagano Prefecture to the Ina Valley and even the Zenkoji Plain (around Nagano City). They had deep ties to the Yamato administration and managed the high-quality horses of Shinano. In the Jinshin War, they received a request from O no Omi Honji (a close aide to Tenmu and father of O no Yasumaro, who later compiled the Kojiki), who was the administrator (Yunomura-no-unagashi) of the Yunomura in Mino Province, which was Prince Oama's private estate (Yunomura were estates given to imperial family members and consorts as an economic base. This name is considered a borrowing of the Chinese imperial private estate system and is not necessarily a hot spring area. Only the Yunomura of Tenmu and Jito appear in records. During the Nara period, it continued as a tax collection right exclusive to the imperial family called the Yunobe). They mobilized the entire clan to organize Shinano cavalry and participated in the war. Emperor Tenmu, having witnessed the cavalry of the eastern provinces in the Jinshin War, carried out reforms after his accession that fundamentally changed Japan's military system.
He began to shift the system to one where the imperial court directly grasped and managed the high-quality horse production areas (maki) in Shinano and Kai, which had previously been privately owned and managed by powerful clans (the maki of the Ritsuryo system). This built a system that could conscript thousands of warhorses by the order of the imperial court in times of emergency. The Emperor declared that "the essence of politics is military affairs," mandated horse riding and armament for all government officials, and established penalties for those who did not own horses.

Nara and Heian Periods
For the imperial court in the Nara and Heian periods, horses were the most important strategic material supporting the nation's military and communications, and were also high-class status symbols. Under the Ritsuryo system, "umaya" (post stations) were placed on trunk roads connecting the capital and the provinces, and official documents were delivered and emergency contacts were made by ringing bells called "ekirei" and changing horses. In addition, the imperial court needed a large number of warhorses to advance the conquest of the Emishi in the Tohoku region. As samurai emerged from the mid-Heian period onwards, mounted archery battles became mainstream.
To secure high-quality horses, the imperial court established the Kumakuryo (Bureau of Horses and Pastures) and created state-run pastures called "kanmaki" throughout the country. In the capital, a government office called the "Sayu Meryo" (Left and Right Bureaus of Horses) was established to manage and raise horses. In particular, "mimaki" (imperial pastures) directly under the Emperor's control were established in the four provinces of Shinano (Nagano Prefecture), Kai (Yamanashi Prefecture), Musashi (Saitama Prefecture/Tokyo), and Kozuke (Gunma Prefecture), where high-quality horses were raised. Every August, a national ritual called "Komahiki" was held, where the Emperor personally inspected excellent horses gathered from imperial pastures across the country in the garden of the Shishinden. Among the Heian nobility, "kurabeuma" (horse racing), where two horses competed for speed, was very popular as a court event and Shinto ritual. Based on the belief that seeing a white horse would ward off evil, a ritual called "Aouma no Sechie" (White Horse Festival) was also held at the New Year. When droughts continued, the imperial court would dedicate "black horses" to the gods to pray for rain, and when they wanted to stop heavy rain, they would dedicate "white or red horses" to pray. This custom was simplified and changed into "horses drawn on wooden boards (ema)," which continues to the present day.

Takeda Cavalry Corps
The Takeda cavalry corps led by Takeda Shingen is known as synonymous with the strongest in the Warring States period. Its formation is deeply linked to the historical background of the lands of Kai and Shinano from ancient times and the innovative military reforms by Shingen.
According to the Engishiki of the Heian period, there were 16 "mimaki" (imperial pastures) in Shinano and 3 in Kai that dedicated horses to the Emperor. The ancient powerful clans (such as pasture supervisors) who managed these pastures gradually armed themselves and grew into samurai bands. The Sanada clan (Shigeno clan) and the Mochizuki clan, who were important vassals of Shingen, were also clans that originally managed vast pastures in Shinano.
By completely bringing Shinano under his control, Shingen succeeded in absorbing the entire network of ancient imperial pastures and the local landowners (descendants of the pastures) who possessed horse-rearing know-how. This completed a foundation that could secure an overwhelming number of horses, said to be several thousand to a maximum of 9,000 cavalry in the entire army at its peak. Recent research suggests that the proportion of cavalry in the Takeda army was about 10% of the total army (almost the same as other daimyo). What was different from other countries was the high quality of the horses and the proficiency of the riders. Shingen did not just have the gathered cavalry fight separately, but polished tactics so that they functioned as a group. Rather than charging all at once with only horses like in modern movies, they actually used hybrid tactics where infantry (spears and bows) who fought on foot and cavalry who launched surprise attacks and pursuits from the side while mounted on horses cooperated closely. The proficiency of this cooperation was the essence of why they were feared by those around them as the strongest cavalry corps.

Battle of Nagashino and Modern Tactics
The Battle of Nagashino (1575) was a turning point in the history of Japanese warfare from medieval individual military power (cavalry) to modern organizational firepower (matchlocks), and its essence is connected to modern military tactics.
The strength of the Takeda cavalry was mobile warfare that utilized the mobility of horses to pierce the enemy's gaps and close the distance at once. In contrast, Oda Nobunaga countered with positional warfare (field fortification), which is the basis of modern warfare.
The Takeda mounted warriors were "all-purpose individuals" who handled movement, reconnaissance, and combat all by themselves, but the Oda army carried out modern organizational operations of "specialization and division of labor by branch." Furthermore, they functioned with "logistics" that systematically procured large quantities of ammunition and gunpowder from commercial cities such as Sakai.