Minamoto no Yoritomo and the Founding of the Kamakura Shogunate

In the fourth year of Jishō (1180), Minamoto no Yoritomo, who had been exiled to Izu Province, took up arms at the behest of Prince Mochihito's mandate. Defeated in the initial engagement at the Battle of Ishibashiyama by Ōba Kagechika's superior forces, he barely escaped with his life. Crossing to the Bōsō Peninsula, he rallied eastern warriors including Chiba Tsunetane and Kazusa Hirotsune, and within mere months had established control over the Kantō region.

Yoritomo's raising of his banner was not simply a military campaign to overthrow the Taira. By guaranteeing eastern warriors their concrete interests—confirmation and security of territorial holdings—he obtained the organized support of the warrior bands. This differed fundamentally from the way the aristocratic (court) government gathered support through the bestowal of imperial favor; it was the germ of a governing structure by warriors, for warriors.

From Dan-no-Ura to the Appointment of Shugo and Jitō

In the third month of Genryaku 2 (1185), the Taira clan was destroyed at the naval battle of Dan-no-Ura. However, the true architect of victory at this moment was his younger brother Minamoto no Yoshitsune; Yoritomo himself remained in Kamakura, devoted to organizing the governance of the east.

Following the destruction of the Taira, Yoritomo obtained authorization from Retired Emperor Go-Shirakawa in the eleventh month of Bunji 1 (1185) to appoint military governors (shugo) and estate stewards (jitō) throughout the provinces, using the pursuit of Yoshitsune as his pretext. This moment is regarded as the decisive turning point in the establishment of the Kamakura Shogunate. The shugo held military and police authority in each province, while the jitō managed the administration of manors and state lands and collected annual tribute. Through this dual structure, the institutional right of warriors to exert actual control over the manors held by the aristocracy and temples was formally guaranteed.

The Significance of Warrior Government and Japanese Sword Culture

Although the warrior class had continued to grow since the late Heian period, actual political power remained in the hands of the regency houses and the insei (retired-emperor) system—a structure controlled by the aristocracy and imperial family. The establishment of the Kamakura Shogunate fundamentally transformed this structure. With warriors seizing political and military power, the conditions were created for the values of the warrior class—the pride of those who carry the sword, reverence for martial valor, the ethics of lord-retainer loyalty—to emerge as norms throughout Japanese society.

The Japanese sword had already been perfected by the late Heian period into its present curved, single-edged form. The Genpei War was dominated by mounted warriors engaging in sword combat, with the long tachi serving as the primary weapon. Once the Kamakura Shogunate stabilized, swordsmiths were organized under the shogunate's protection, and the Kamakura period became the golden age of the Japanese sword.

The great swordsmiths celebrated in later ages as masters of the "age of celebrated swords"—Masamune (Sōshū tradition), Kuniyuki (Rai school), Ichimonji (Bizen Ichimonji), and Kunimune (Bizen Kunimune, mid-Kamakura)—flourished precisely during this Kamakura and Nanbokuchō period. Through the shogun–gokenin system, the shogunate ritualized the sword as "proof of lord-retainer relationship," and the bestowal of celebrated blades became a symbol of political authority.

Yoritomo and the Sword

Yoritomo himself was known as a patron of swordsmiths. Having organized the rituals of warriors at Tsurugaoka Hachiman Shrine, Yoritomo contributed greatly to establishing a ritual order that placed the sword at the spiritual center of the warrior class. Together with the Minamoto white banner, the sword became a symbolic center of the Kamakura warrior.

Among the swords later called the "Five Legendary Swords"—Dōji-kiri Ansatsu, Onimaru Kunitsuna, Mikazuki Munetsugu, Daitenta Mitsusada, and Juzumaru Tsunetsugu—the Onimaru Kunitsuna was transmitted through the Hōjō clan (the regency family) and is discussed in connection with the Kamakura shogunate. Kunitsuna was a swordsmith of the Awataguchi school active in the Kamakura period, representing the advancement of swordsmith techniques under the rule of the shogunate.

The Gokenin System and the Ritual Status of the Sword

The "gokenin" system established by Yoritomo was based on the mutual obligation of service and beneficence. In return for the gokenin's service to the shogun at the risk of their lives, the shogun guaranteed their territorial holdings and demonstrated his favor through the bestowal of swords, armor, and horses. In this context, the sword transcended mere weaponry to become "an object embodying the bond with one's lord," and the careful preservation and transmission of a sword received from one's master became the essential duty of a warrior.

This practice spread throughout warrior society and developed over the Muromachi, Sengoku, and Edo periods into a culture of preserving "bestowed tachi" as family treasures. That the majority of celebrated swords surviving to the present day carry provenance reading "received from [someone]" is a direct legacy of the ritual order established in the Kamakura period.

The Completion of the Shogunal System

Through the subjugation of the Ōshū Fujiwara in Bunji 5 (1189), Yoritomo brought the Tōhoku region into his domain, completing the first warrior government to exercise effective control over all of Japan. In Kenkyū 3 (1192), he was appointed Sei-i Taishōgun, completing the "shogunate" in legal terms.

However, historically, the appointment of shugo and jitō in 1185 is generally regarded as the true beginning of warrior government. The conventional wisdom of the academic world has shifted from the traditional wordplay "in the good year 1192, the Kamakura Shogunate was built" to "in the good year 1185, the Kamakura Shogunate was built," a change that reflects a re-evaluation of the significance of the appointment of shugo and jitō.

The establishment of the Kamakura Shogunate was the opening of an era lasting approximately seven hundred years in which warriors became the protagonists of Japanese society, and the starting point of the long history in which the Japanese sword ascended from mere weapon to become a cultural symbol at the core of bushidō, the arts, and ritual life.