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Tengyō 2–4 (939–941)
Seto Inland Sea coasts, Iyo Province, Dazaifu (present-day Shikoku and Kyushu)
Forces
Fujiwara no Sumitomo's Forces (Rebels)
Imperial Punitive Forces
About 17 min read
Fujiwara no Sumitomo's Rebellion (Fujiwara no Sumitomo no Ran) was an armed uprising that Fujiwara no Sumitomo, a former provincial governor of Iyo Province (present-day Ehime Prefecture), organized by mobilizing pirate bands throughout the Seto Inland Sea between Tengyō 2 (939) and Tengyō 4 (941). Together with Taira no Masakado's Rebellion, which erupted in the Kanto region during the same period, it is collectively known as the "Shohei-Tengyō Disturbances" (Shohei-Tengyō no Ran). These two rebellions represent the first large-scale instance in 10th-century Japan—when the ritsuryō state's actual administrative capacity was collapsing—of regional warriors and armed groups challenging central authority, and are positioned as historical harbingers of the later emergence of samurai military governments (the samurai age).
Fujiwara no Sumitomo was born as the son of Fujiwara no Yoshinori, a cadet branch of the Fujiwara Northern House (Fujiwara Hokke). Around the 930s, he was dispatched to Iyo Province as Vice Governor (Suke, the second-ranking official). During his tenure, he was responsible for conciliating and suppressing pirate bands infesting the Seto Inland Sea. While functionally performing the duties of the "Tsuibushi" (pursuit officers) established by the ritsuryō state, he built deep connections with maritime powers in the Seto. After his term ended, instead of returning to the capital, he became the commander of pirate bands. Various theories exist regarding why Sumitomo chose rebellion, but scholars attribute it to the frustration of a cadet-branch Fujiwara with limited prospects for advancement in central politics, the accumulation of military power in the provinces, and his deep involvement with pirate groups.
The 10th-century Seto Inland Sea, coinciding with the collapse of the equal-field (handen) system and tax structures under the ritsuryō order, appeared as a "maritime lawless zone" into which impoverished peasants and fallen warriors streamed. Sumitomo organized these wandering armed bands, and at his peak commanded several thousand troops and hundreds of vessels, forming a major naval force. Sumitomo's command, which controlled harbors and straits throughout the Seto region, is called Japan's first "mizugun" (water army) and can be regarded as a distant precursor to the later Murakami and Mōri naval forces prominent during the Sengoku period.
In late Tengyō 2 (939), Sumitomo's forces successively attacked and captured provincial government seats (kokufu) along the Seto Inland Sea coasts in Iyo, Sanuki, and Awa, driving out provincial governors. The court dispatched pursuit officers, but they could not easily suppress Sumitomo's forces, which were proficient in the Seto's terrain and naval warfare. In December Tengyō 2 (940), they burned the Awaji provincial government seat, and in the following Tengyō 3 (941) extended their power toward Bizen and Harima. Some historical sources indicate that Sumitomo's forces reached areas near the provincial seats of Settsu and Kawachi, throwing the court into direct terror.
In May Tengyō 4 (941), Sumitomo's forces crossed to Kyushu and captured and burned Dazaifu (present-day Dazaifu City, Fukuoka Prefecture). Dazaifu was the administrative, military, and diplomatic center of western Japan; its fall dealt a serious shock to the court. The court, thrown into turmoil, hastily assembled a powerful suppression force. Under the command of Pursuit Officers Ono no Yoshifuru and Minamoto no Tsunemoto, the imperial forces were dispatched and annihilated Sumitomo's army in naval battles off Iyo and Hakata. Sumitomo himself was soon captured and died in prison (or was executed).
One reason Fujiwara no Sumitomo's Rebellion holds crucial significance in sword history is that this period marks the transition from ritsuryō "gundan" (conscripted military units) to "bushi-dan" (private warrior bands). Under the ritsuryō conscription system, soldiers carried standardized weapons—straight swords and bows—supplied by the state. However, as the ritsuryō military system collapsed, provincial magnates and warriors armed themselves with self-procured swords and armor, forming private armed bands.
This late 10th century overlaps with a critical period in Japanese sword evolution: the progression from "warabi-te-katana" to "kebuki-gata tachi" and, by the mid-Heian period, to the "shinogi-zukuri tachi" (the mature form of the Japanese sword). The swords carried by warrior bands participating in Sumitomo's and Masakado's rebellions represented an opportunity to test transitional sword-making techniques in actual combat. Particularly, the curved tachi designed for mounted combat proved its practicality in Seto Inland Sea naval engagements and Kanto field battles. Naval warfare in Sumitomo's Rebellion, conducted in the unique environment of close combat on wave-tossed ships, demanded weapons and techniques adapted to these conditions; lightweight tachi with excellent maneuverability were highly valued, it is believed.
Minamoto no Tsunemoto, who suppressed Sumitomo's forces, is positioned as the ancestor of the Seiwa Genji line and the patriarch of the samurai. Tsunemoto's descendants established samurai status during the 10th to 12th centuries, eventually leading to Minamoto no Yoritomo's founding of the Kamakura bakufu (1185–). Within this lineage, the swords wielded by the Seiwa Genji held symbolic significance as the "Genji blade" and greatly contributed to the later formation of the concept of "samurai swords" in sword culture. The military rise of the Seiwa Genji—Tsunemoto, Minamoto no Mitsunaka, Minamoto no Yorinobu, Minamoto no Yoriyoshi, and Minamoto no Yoshiie—was inseparable from the refinement of swords in each generation.
Regarding the weapons used by pirates participating in Sumitomo's Rebellion, bows, naginata, straight swords, and tachi likely existed in mixed armaments. The 10th-century pirates favored the "suikan-koshigata-na" (water-robe hip sword), a short, easily handled blade suited for close combat in confined ship spaces. This can be interpreted as an early manifestation of later "wakizashi" (short sword) culture. The pirate culture of the Seto Inland Sea possessed a practical, combat-oriented sword philosophy distinct from land-based ritsuryō weapon culture, valuing functional cutting edge and durability over formal ritual and rank. This maritime warriors' sword philosophy was inherited by water army commanders during the Muromachi and Sengoku periods, forming the unique character of Seto Inland Sea sword culture.
Sumitomo's and Masakado's rebellions, occurring nearly simultaneously in the east and west, symbolize a turning point in Japanese history as two massive armed uprisings. Through suppressing these two rebellions, the court established a policy of publicly recognizing and utilizing regional magnates and warriors as military forces. Warriors who distinguished themselves as pursuit officers gained both court positions and actual control over regional governance. This process became the embryo of later samurai military governments and marks the starting point of the long historical current leading to the establishment of the Taira regime and Kamakura bakufu in the late 12th century.
From the sword's perspective, Sumitomo's Rebellion marks the end of the era of "state-controlled swords" managed by the ritsuryō state and the emergence of a "private sword culture" cultivated and possessed by individual warriors. With the collapse of the ritsuryō system, swords underwent a fundamental historical transformation: from "state weapons" to "samurai personal soul and pride." This epochal change in sword meaning began during the 10th century. The Shohei-Tengyō Disturbances opened the door of history through which swords underwent the great transition from public property to personal weapons, an event deeply inscribed at the foundation of Japanese sword history.
Following the suppression of Fujiwara no Sumitomo's Rebellion, during the Heian mid- to late period (10th–12th centuries), Japanese sword culture developed rapidly. With the rise of warrior bands, sword smiths across the regions competed with one another, laying the foundations of the "Five Transmitted Schools" (Go-Kaiden): Yamashiro, Yamato, Bizen, Soshu, and Mino traditions. Particularly during the Heian late period, sword smiths of Kyoto (Sanjō Munechika, Gojo Kuniie, and others) produced numerous masterworks that later generations would revere as the pinnacle of samurai sword culture as an art form. The "Mikazuki Munechika" (Crescent Moon Munechika), attributed to Sanjō Munechika, is counted among Japan's Five Heavenly Swords and represents the apex of the Japanese sword achieved roughly two centuries after Sumitomo's Rebellion in the late Heian period. Moreover, the works of Bizen smiths—Tomonari, Masatsune, and others active during the late Heian—became the foundation for the Bizen Osafune production center's rise and established the technical base enabling mass production of Japanese swords during the Kamakura and Muromachi periods. There is no doubt that the historical upheaval triggered by Sumitomo's Rebellion—the collapse of the ritsuryō system and the rise of the warrior class—was one of the fundamental driving forces that elevated the Japanese sword to the heights of artistic and spiritual culture.