Yamamoto Kansuke's Treasured Blade and Sword Collections—A Study of the Weapons Worn by Takeda Shingen's Military Advisor and the Sengoku Warlord's Perspective on Swords

Who Was Yamamoto Kansuke?

Yamamoto Kansuke is known as a military strategist and military theorist of the Sengoku period who served Takeda Shingen. While various theories exist regarding his birth and death years, it is said that he was killed in the Fourth Battle of Kawanakajima in 1561 (Eiroku 4). Since his appearance in formal historical records is limited to the "Kōyō Gunkan," questions about his existence and biographical details have long been subjects of debate. In recent years, the portrayal in the 2006 NHK historical drama "Wind, Forest, Fire, Mountain" has become widely known, making him one of the most popular warlords among Sengoku enthusiasts.

However, when it comes to "Yamamoto Kansuke's beloved sword," historical records offer little explicit information. In this article, we will clarify the likely appearance of the sword Kansuke used by examining the styles of blades worn by military advisors and strategists of the time, the Takeda clan's sword culture, and the context of the Battle of Kawanakajima.

The "Sword-Wearing Styles" of Sengoku Warlords—Swords of Military Advisors and Ashigaru Captains

In the Sengoku period, the swords worn by warlords served two main purposes: first, practical combat use, and second, ceremonial and formal occasions.

In actual combat, primarily uchigatana (打刀, straight-draw swords) were used. From the mid-Muromachi period onward, the style of mounted warriors wearing swords at the waist—the "sashi-soe" style—became widespread, and the more easily drawn uchigatana became the primary choice over the longer tachi. A blade length of two shaku two sun to two shaku four sun (approximately 66–73 cm) was considered practical, and shapes suited to quick drawing in battle were preferred.

Yamamoto Kansuke's rank is thought to have been close to that of a "samurai captain" or "ashigaru captain," and the swords worn by this class at the time had the following characteristics:

• Blade length: Two shaku two sun to four sun (a practical combat length)
• Curve: Shallow curve (inner or medium curve) in uchigatana style
• Smithing tradition: The Mino and Bizen traditions were widely used among Sengoku warlords, making Mino-forged blades a likely choice due to their availability
• Fittings: A practical mounting with a black-lacquered scabbard and protective metal guards

While tachi were worn on ceremonial and formal occasions, it is reasonable to assume that for someone of Kansuke's position, the uchigatana suited to daily command and movement was the primary blade.

The Kōyō Gunkan and the Takeda Clan's Sword Culture

The "Kōyō Gunkan" is a document close to a primary source transmitting information about the Takeda clan's military affairs and culture, and contains descriptions of swords throughout. Takeda Shingen highly valued swords, and the document records the practice of granting fine blades to retainers as rewards for battle.

Of note among the smithing lineages valued by the Takeda clan is the Kōshū smithing tradition. Blade smiths based in Shinano and Kai were not as nationally renowned as those of Bizen and Mino, but were distinguished by their practical, durable forging and were highly valued by local warlords. It is entirely possible that a warlord of Kansuke's rank possessed a blade forged by local Kōshū smiths. Furthermore, Takeda Shingen himself was a collector of fine swords, and records exist of blade gifts exchanged during his communications with Uesugi Kenshin. It is not impossible that Kansuke, as a military advisor in close attendance to Shingen, wore a blade granted to him by his lord.

The Battle of Kawanakajima and Kansuke's Final Hours—Swords and Death in Battle

The Fourth Battle of Kawanakajima in 1561 (Eiroku 4) was one of the greatest decisive battles of the Sengoku period, where the armies of Takeda and Uesugi clashed. According to the "Kōyō Gunkan," Yamamoto Kansuke was mortally wounded while attempting to break through a circular encirclement in this battle and was killed. On the battlefield, the sword was the weapon of last resort for individual combat. Whether Kansuke actually drew his sword in combat is unknown, but it was common for officers of his rank to make a final stand with their blades when falling in battle. This reminds us that the swords of the Sengoku period were not mere ornaments but practical tools through which men literally staked their lives.

The Authenticity of Swords Associated with Kansuke in Modern Times

Multiple swords claimed to have been used by Yamamoto Kansuke exist in museums and local historical museums throughout Japan, but most remain "tradition-transmitted pieces" whose provenance is difficult to verify. Japanese swords' lineage and significance are prone to be preceded by oral tradition, reflecting a cultural tendency to associate them with famous warlords. The following are checkpoints for verifying authenticity:

1. Certification: Has it been examined by the NBTHK (Japanese Society for the Preservation of Art Swords)?
2. Production date consistency: Do the inscriptions, blade patterns, and steel composition align with the period when Kansuke lived (early 16th century)?
3. Provenance documents: Do written records of transmission exist from the early modern period onward?
4. Smith lineage consistency: Does it match the sword-smithing lineages actually in circulation in the Shinano-Kai region at the time?

Without meeting these criteria, it is difficult to definitively identify a sword as "Kansuke's blade." However, the preservation of swords traditionally attributed to Yamamoto Kansuke as local cultural assets has value in transmitting interest in Sengoku warlords to future generations.

Warlords' Perspectives on Swords—The Meaning Kansuke Found in His Blade

Yamamoto Kansuke is said to have been a military strategist who prioritized cunning and strategy over brute military force. Yet the sword remained the spiritual pillar of the samurai, and as a member of the Takeda clan, he lived within the realm of blade culture. For Sengoku warlords, the sword was not merely a weapon but a pledge of loyalty to the lord and an embodiment of samurai honor. If Kansuke possessed a blade granted by Shingen, it was also proof of their master-servant bond. When contemplating Kansuke's life, the sword he wore shines quietly as a symbol connecting his pride as a warrior to his final moment.