The Keicho Campaign (1597–1598) and Japanese Swords: How Toyotomi's Second Korea Invasion Impacted East Asian Sword Culture

The Korean Invasions and Japanese Swords — Background of Two Campaigns

Toyotomi Hideyoshi conducted large-scale invasions of the Korean Peninsula twice: in 1592 (Bunroku 1) and 1597 (Keichō 2). The former is called the Bunroku Invasion, the latter the Keichō Invasion. This essay particularly focuses on the Keichō Invasion (1597–1598) and explores the traces this war left on the history of the Japanese sword.

The Keichō Invasion was a renewed offensive following the breakdown of ceasefire negotiations in the Bunroku Invasion. The Toyotomi forces mobilized over 140,000 troops, and from Busan as a base, controlled the southern part of the peninsula. However, following Hideyoshi's death in August 1598, the Japanese military was forced to withdraw, and the war ended in a virtual draw.

The Surge in Sword Demand During the War

The period of the Korean invasions was also the time when the sword-making industry, which had matured through the Sengoku period, entered its final phase of mass production.

Mass orders for quantity-produced swords: From a logistics standpoint, there was no room to equip individual samurai with high-quality custom-made swords. Sword makers centered in Bizen and Mino produced large quantities of so-called "quantity-produced swords" (kazuuchi-mono). Although individual quality varied, practical cutting performance was ensured.

Mobilization of renowned sword smiths: Meanwhile, daimyo and officer-class warriors were supplied with fine custom-made blades. Surviving dated swords from the Keichō period bearing date inscriptions (such as "Keichō 2") reflect the war demand of this era.

Japanese Swords Lost to Foreign Lands — The Reality of Overseas Dispersal

Combat on the Korean Peninsula was fierce, and numerous Japanese swords were left behind on the battlefield. The pathways of dispersal can be classified into several categories.

• Loss and abandonment during combat: Many swords were left behind during retreat. These swords, recovered by Korean and Ming forces, were called "wado" (倭刀, Japanese swords) and stored in Korean armories.
• Seizure from surrender and captives: Swords worn by Japanese soldiers who surrendered in combat were confiscated.
• Technology transfer by Korean sword smiths: Some records suggest that Japanese blacksmith craftsmen taken as captives were held in Korea and transmitted their techniques. In ceramics, records of craftsmen transported to Korea as "pottery founders" are well-known, but similar cases are said to have occurred among blacksmith craftsmen as well.

"Wado" Remaining in Present-Day Korea and China

Today, Korean national museums and folklore museums preserve Japanese swords estimated to be from the Keichō Invasion era. These are classified as "wado" and some have been confirmed to be works of Japanese sword smiths.

In China as well, Japanese swords recovered by Ming forces from combat in Korea partly survive, and are said to be included in museum collections in Beijing and Nanjing. However, detailed investigation and public disclosure remain limited, and much remains unclear.

What the Keichō Invasion Left in Sword-Making Cultural History

After the war's end, the sword-making industry changed rapidly.

Sharp decline in demand and closure of sword smiths: The Bizen sword-making community that supported the mass production system suffered a devastating blow from the disappearance of war demand and the arrival of the "era of peace" with the establishment of the Edo shogunate in 1603. Notably, the Bizen and Osafune region had already suffered a catastrophic impact from a major flood of the Yoshii River (the Kumayama debris flow) in Tensho 18 (1590), before the Korean invasion, resulting in the death and closure of many sword smiths. The disappearance of war demand dealt a further blow to the subsequent decline of the Osafune school.

Transition to the Shintō era: From the late Keichō through the Genwa period, sword style transitioned from "kotō" (old swords) to "shintō" (new swords). According to some views, actual combat experience from the Korean invasion (demands regarding sword cutting performance and shape) influenced this turning point.

Reciprocal cultural influence: While Japanese swords dispersed to the Korean Peninsula, many technologies and cultural goods were brought from Korea to Japan (ceramic techniques, books, and the like). Regarding swords, there are many unidirectional influence relationships, but overall cultural exchange possessed complex bidirectional character.

Conclusion

From the perspective of sword history, the Keichō Invasion can be positioned as "the war that accelerated the end of the kotō era." The fact that vast numbers of Japanese swords were dispersed abroad and remained on the Korean Peninsula and in China as "wado" demonstrates that the Japanese sword transcends mere domestic cultural property and forms part of the broader cultural history of East Asia.

Historical Context of the Tensho 18 Flood and the Osafune School

After Bizen Osafune suffered the catastrophic blow of the great flood in Tensho 18 (1590), it was still able to respond to the enormous sword demand of the Korean invasion (1592–98) thanks to the resilience of Osafune-school sword smiths scattered across the region and the active sword-smith recruitment policies of daimyo. The triple waves of Tensho flood → invasion demand → disappearance of demand caused the Osafune school to rapidly decline from the largest production center of the kotō era. This process should be understood as the historical background making Bizen-den swords rare in today's market.

Bizen-den swords currently maintain high evaluation in the sword market, and old swords authenticated as Osafune-school works become subjects of collection after careful confirmation of authenticity and preservation condition. The traces carved by the Yoshii River great flood of Tensho 18 into early modern sword history run deep, and among researchers, the practice of dividing "Bizen swords before" and "the post-flood reconstruction period" using this flood as a demarcation point remains robust.