Koji Era
弘治（こうじ）
The Koji era (1555–1558) fell between Tenbun and Eiroku, spanning the reign of Emperor Go-Nara into Ogimachi under shogun Ashikaga Yoshiteru. In Koji 1 (1555), Takeda Shingen and Nagao Kagetora (later Uesugi Kenshin) faced off for roughly 200 days across the Sai River in Shinano — the Second Battle of Kawanakajima — before reconciling through the mediation of Imagawa Yoshimoto. Sword-ranking sources place the Ise-Kuwana smith Muramasa at the sue-koto chu-jo-saku grade during this era.
Description
Koji as an Era Name
The Koji era fell between Tenbun and Eiroku, running from October 23, 1555 to February 28, 1558. During this span, the throne passed from Emperor Go-Nara to Emperor Ogimachi, while Ashikaga Yoshiteru held the Muromachi shogunate. It was an era in which Sengoku-period warfare continued to deepen.
The Sai River Standoff at Kawanakajima
In Koji 1 (1555), Takeda Shingen of Kai and Nagao Kagetora of Echigo (later Uesugi Kenshin) faced off across the Sai River in Shinano Province in a dispute over the Kawanakajima plain. The two armies remained in a standoff for roughly 200 days before reaching a reconciliation mediated by Imagawa Yoshimoto of Suruga. This confrontation, later remembered as the second of the five engagements collectively known as the Battles of Kawanakajima, stands as one of the defining military events of the Koji era. The prolonged standoff also serves as circumstantial evidence of the sustained, large-scale demand for combat-ready blades and arms among contemporary warlords.
Muramasa's Sue-Koto Chu-jo-saku Ranking
Sword-ranking reference sources place the Ise-Kuwana smith lineage Muramasa at the sue-koto chu-jo-saku grade during the Koji era. Muramasa would later become widely known through later-era legends linking the lineage to the Tokugawa house (the so-called "cursed blade Muramasa" tradition), but the Koji-era ranking itself is a contemporary documentary record of the lineage's technical standing during the sue-koto period.
Position in Sword History
The Koji era is characterized by two geographically distinct facts occurring under the same short reign name: the Kawanakajima standoff over Shinano Province, and the contemporary ranking of the Muramasa lineage's craftsmanship. Together they offer a cross-section of arms demand and swordsmith evaluation in the middle Sengoku period.
The Course of the Standoff and Wartime Demand for Arms
In the fourth month of Koji 1, Takeda Shingen marched from Kai into Shinano, supporting the Kurita clan holding Asahiyama Castle in an effort to secure the Zenkoji plain. In response, Nagao Kagetora entered Shinano that same seventh month, positioning his forces at Yokoyama Castle near Zenkoji temple and attacking the Takeda-aligned Asahiyama Castle. The two armies remained in a standoff across the Sai River for roughly 200 days without a decisive engagement, until reconciliation was brokered by Imagawa Yoshimoto. Such a prolonged standoff reflects the underlying pressure on both sides to continuously procure and maintain combat-ready blades and arms for their forces — a concrete military circumstance unfolding under the Koji era name.
The Muramasa Lineage and Sue-Koto Evaluation
Muramasa was a lineage of smiths based in Kuwana, Ise Province, counted among the representative smiths of the sue-koto period. The ranking of Koji-era Muramasa work at the sue-koto chu-jo-saku grade in ranking reference sources constitutes a contemporary record of craftsmanship evaluation, one that should be understood separately from the later legendary tales linking the lineage to the Tokugawa house.
Characteristics of This Era
- Koji (1555–1558), between Tenbun and Eiroku in the mid-Sengoku period, spans the reigns of Emperor Go-Nara into Ogimachi under shogun Ashikaga Yoshiteru
- In Koji 1 (1555), Takeda Shingen and Nagao Kagetora faced off across the Sai River in Shinano for roughly 200 days (Second Battle of Kawanakajima), reconciled through Imagawa Yoshimoto's mediation
- The prolonged standoff offers circumstantial evidence of sustained wartime demand for combat-ready blades and arms
- Sword-ranking references place the Ise-Kuwana Muramasa lineage at the sue-koto chu-jo-saku grade during the Koji era
- The era is distinguished by two geographically distinct, contemporaneously recorded facts — the Kawanakajima campaign and the Muramasa ranking