Swords in Mid-to-Late Heian Japan: The Rise of the Warrior Class and the Tachi

The Birth of the Japanese Sword—From Straight Swords to Curved Blades

The mid-Heian period (9th-10th centuries) was one of the most fundamental turning points in the history of the Japanese sword. Before that time, swords of the Nara period and early Heian period were called "straight swords" (chokuto), which were linear blades strongly influenced by the continent (Tang China). Single-edged or double-edged linear forms resembling swords or short swords were the mainstream. However, from the 9th to 10th centuries, blades with a distinctive Japanese "curve" (sori) began to emerge rapidly.

Behind this change lay the establishment of a uniquely Japanese combat style. While straight swords were advantageous in continental infantry combat, in mounted horseback warfare in the mountainous and forested battlefields where Japanese samurai fought, curved blades were far better suited for actions such as the diagonal "kesagiri" cut and "noutentouzhiku" strike performed from horseback. Furthermore, in the action of drawing the sword from the waist—"battou"—the curve allowed the blade to be drawn smoothly from the scabbard (saya).

Swords with this curve are called "tachi." The basic style of the tachi was to wear it suspended from the waist with the edge facing downward (haiyo), and its elegant curve, reaching 70-80cm or more in blade length, perfectly combined functional beauty with practicality. The maximum curve, called "koshizori," located near the base of the blade, is characteristic of the Heian period. This form of tachi became the mainstream form of the Japanese sword for the next 400 years.

The Rise of the Eastern Warriors—Real Combat Hones the Sword

In the 11th century, the "Zenkunen War" (1051-1062) and the "Gokennen War" (1083-1087), which took place in Mutsu Province (present-day Tohoku region), were campaigns in which the eastern warrior clans, centered on the Minamoto clan, first experienced large-scale combat.

The Minamoto clan forces, led by father and son Minamoto no Yoriyoshi and Minamoto no Yoshiie, proved their prowess as an organized military force through these two campaigns. Yoshiie, who held the epithet "Hachiman Taro," is remembered in later generations as a military leader who established a combat method combining mounted archery tactics with the tachi. In this process, the performance of swords that could withstand real combat—the three conditions of "not breaking, not bending, and cutting well"—were specifically tested.

Swords of this era had a cross-sectional structure called "shinogizukuri," and through a ridge line called "shinogi" running down the center of the blade, they achieved high rigidity while remaining thin and lightweight. The relationship between iron-producing regions in the northeast (around Iwate and Akita prefectures) and sword makers is believed to have begun around this period, and the prototype of the eastern warrior region's distinctive sword culture was formed during this era.

The Wavering Imperial Court Power—The Samurai Come to the Fore in Politics

The "Hogen Rebellion" (1156) and the "Heiji Rebellion" (1159) in the mid-12th century were epoch-making events in which samurai came to the forefront of politics as a result of internal court disputes.

In the Hogen Rebellion, Minamoto no Yoshitomo and Taira no Kiyomori fought for Emperor Go-Shirakawa, while Minamoto no Tameyoshi and Minamoto no Tametomo fought for retired Emperor Sutoku. Minamoto no Tametomo, feared for his prodigious strength and archery skills, held the epithet "Chinzei Hachiro," and his military reputation echoed as far as Kyushu. In the Heiji Rebellion, Minamoto no Yoshitomo was defeated by Taira no Kiyomori, and Yoshitomo's son, Minamoto no Yoritomo, was exiled to Izu. Through this rebellion, Taira no Kiyomori seized actual political power, and the golden age of the Taira clan government arrived.

During this period, demand for swords increased rapidly. Taira no Kiyomori actively promoted Japanese-Song trade, and while Chinese iron and technology flowed into Japan, Japanese sword makers fused these with their own traditional techniques and instead achieved development based on Japan's unique aesthetic sensibilities. Sword makers from Yamashiro Province (Kyoto) and Bizen Province (Okayama) began receiving numerous orders, and competition between production centers and technological advancement were promoted.

The Minamoto-Taira War—The Japanese Sword Becomes History's Leading Role

The Minamoto-Taira War (1180-1185; also known as the Jisho-Juei Rebellion) was a large-scale civil war in which the Minamoto of the east and the Taira of the west fought for control of the realm. This series of conflicts—at Fuji River, Ichinotani, Yashima, and Dan-no-ura—made the practical combat role of the Japanese sword known throughout the land.

The numerous celebrated swords that appear in the Tale of the Heike (Heike Monogatari) reflect the deep attachment to swords in this era. "Kogarasu-maru" is a treasured sword passed down in the Taira clan, with a mythical story that it was granted by Inari Myojin. "Usui Midori," said to be the beloved sword of Minamoto no Yoshitsune, is also told to have been granted by Kiichiho-gan. In scenes such as Nasu no Yoichi shooting at a fan target and Yoshitsune's "Hassou Tobi" (eight-boat leap)—the sword, as a symbol of the warrior, was always present behind these scenes.

The culture of "kubi-jikken" (head inspection) on the battlefield, the custom of presenting swords to generals as war rewards, and the ritual of "tachiarai" (sword washing)—all of these were established in the late Heian period and became the cultural foundation that positioned the Japanese sword as a spiritual symbol beyond merely a weapon.

The Sword Makers of the Heian Period—The Dawn of Three Great Production Centers

While records regarding sword makers of the Heian period are fragmentary, it can be confirmed that Yamashiro, Yamato, and Bizen provinces were already functioning as major sword-producing centers.

The Fulfillment of the Late Heian Period—The Spiritual Foundation of Warrior Culture

The sword culture of the mid- and late-Heian periods was a preliminary stage leading to the golden age of the Japanese sword in the Kamakura period. The completion of the curved tachi, the real-world combat experience of the eastern warrior clans, and the internal conflict between the Minamoto and Taira—through the accumulation of these historical experiences, the concept of the Japanese sword as the "soul of the warrior" came into being.

Technically, distinctive Japanese sword characteristics such as "shinogizukuri," "koshizori," "bo-hi," and "choji-midare" were established during this period, and purely Japanese aesthetic beauty of sword blades freed from continental influence was coming to completion. The foundation for the three production centers of Yamashiro, Yamato, and Bizen to hone their skills through friendly competition and each form their own distinctive "tradition" (den) was also cultivated during this era.

In the late Heian period, where the aesthetic sense of "mono no aware" (pathos of things) intersected with the harsh reality of the warrior—the shape of the tachi, tracing a gentle arc, may have been that which best embodied the spirit of that age. The Heian sword, beyond its physical existence, formed the spiritual foundation of Japanese warrior culture.