Continental Sword Imports in the Asuka Period: Tang and Baekje Blade Technology

The Asuka Period and Continental Culture Currents——The "Import Era" in Sword History

When discussing the history of Japanese swords, the narrative typically begins with the curved blade (swords with a bend or *sori*) known as the *tachi* that emerged during the Heian period. However, the history of swords in Japan began far earlier than that, and the Asuka period (approximately 592–710) is positioned as a particularly noteworthy "period of active import of continental technology."

Centered on the reigns of Empress Suiko (r. 593–628) and Prince Shotoku, Japan actively pursued diplomatic and cultural exchange with China's Sui and Tang dynasties and with the kingdoms of Baekje, Goguryeo, and Silla on the Korean Peninsula. International relations during this era went beyond mere political contact, constituting a vast project to transplant advanced civilizational elements—including metallurgical technology, forging techniques, and Buddhist culture—to the Japanese archipelago.

This article examines the sword-making technology that flowed into Japan from the continent during the Asuka period and the influence it exerted on the subsequent development of the Japanese sword.

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Before the Asuka Period——Sword Conditions in the Kofun Period

To understand the imports of the Asuka period, we must first understand the circumstances of the preceding Kofun period (late 3rd century to around 7th century), which provides the necessary context.

During Japan's Kofun period, large numbers of iron swords and iron blades were unearthed as grave goods. Notable examples include the gold-inlaid iron sword discovered in the Inari Shrine Kofun in Saitama Prefecture (a National Treasure) and the iron blade from the Eda Funayama Kofun in Kumamoto Prefecture. All of these were **straight swords (*chokutō*)****——blades without curve, perfectly straight——and were heavily influenced by the *tōshi* and *kantō-tachi* (ring-pommel swords) that were widely manufactured on the continental mainland and Korean Peninsula.

Iron production during the Kofun period was largely carried out by immigrant metalworkers and blacksmiths from the Korean Peninsula, and Japan's indigenous forging techniques were still in their infancy. Technology transfer from the continent essentially supported Japan's iron industry during this era.

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Suiko Era Diplomatic Policy and Technology Importation

Dispatch of Missions to Sui and Tang

Under Prince Shotoku's leadership, the Suiko court dispatched the first mission to Sui in 607 (headed by Ono no Imoko). After Sui's fall, this continued with missions to Tang (with the first dispatch in 630), continuing throughout the Nara period.

The purpose of these missions to Sui and Tang went beyond merely seeking political recognition. The accompanying students and Buddhist monks studied China's ritsuryo bureaucratic system, Buddhism, Confucianism, medicine, and astronomy, and returned home with knowledge of craft techniques and metal-working technology as well.

Particularly noteworthy is Tang-period sword-making technology. Tang swords, known as *kara-tachi* and *karayōshi*, represented the world standard of their time in steel refining and heat-treatment techniques.

Technology Transfer from Baekje

Running parallel to the missions to Sui and Tang was the important direct technology transfer from Baekje (in what is now the western Korean Peninsula).

From the late 6th century through the early 7th century, Baekje maintained close ties with Japan as a conduit for Buddhist culture. According to historical records, among the technicians who came to Japan in connection with the official introduction of Buddhism in 552 (or 538) were **blacksmiths (*kajishi*)**.

The Nihon Shoki contains multiple entries indicating that *keironron* (Buddhist texts) and "technical experts" were sent from Baekje. These immigrant blacksmiths were organized as the *kanuchihe* (blacksmith's guild) and produced weapons, agricultural tools, and implements under the Yamato administration.

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The Content of Sword-Making Technology Imported During the Asuka Period

Steel Refining Technology

Before the Asuka period, iron production in Japan centered on forging **sponge iron (*kaimen-tetsu*)** obtained by reducing iron sand at low temperatures. This method produced iron with unstable carbon content and made it difficult to produce uniform steel.

Among the technologies transmitted from the continent were early forms of **blast furnace (*kōro*) technology and techniques for controlling carbon content to produce steel (*haganē*)**. During the Tang period in China, a refining method called "hundred-times refined steel" had been developed, and techniques for repeatedly forging iron to remove impurities and obtain high-quality steel were well-established.

This technology would later become the prototype for the distinctly Japanese *tatara* iron-smelting technology.

Early Forms of Heat-Treatment (Heat-Hardening) Technique

One of the defining features of the Japanese sword is "heat-treatment"——the technique of hardening the blade edge by rapid cooling——and the primitive forms of this heat-treatment technique are believed to have been introduced through technology transfer from the continent.

During the Tang period in China, a primitive form of "*dōoki*" (applying clay)——covering the blade with clay without covering the edge, then rapid cooling to harden only the edge——was known. When this technique came to Japan and underwent independent development, it became a precursor to the *hamon* (blade pattern) that Tang-period master smiths would eventually perfect.

Development from Ring-Pommel Swords to Flat Swords

Examining swords excavated from the Asuka period, we find numerous examples of the **ring-pommel sword (*kantō-tachi*)**——ceremonial great swords featuring a ring-shaped metal fitting (the ring-pommel) at the pommel——that Japan adopted from designs widely manufactured in Baekje, Silla, and Goguryeo.

The ring-pommel functioned as a symbol of power and was bestowed upon Yamato clan nobility and immigrant leaders. In Buddhist temples from the Asuka period that have survived, such as Hōryū-ji and Shitennō-ji, the continental influence is evident in their sword collections.

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The Sword Standard Seen in the Shōsōin Treasures (Asuka–Nara Period)

The technological accumulation of the Asuka period culminated in the Shōsōin treasures of the Nara period. The Shōsōin houses not only swords that arrived from Tang but also straight swords manufactured in Japan, which serve as invaluable documents demonstrating the level of metal-working technology in Japan during the Asuka–Nara periods.

Many of the Shōsōin swords are ornate, with handles and sheaths decorated in lacquer, wood, leather, and metal fittings, suggesting they were "ceremonial and gift items" rather than "practical combat weapons." This indicates that the "imports" of the Asuka period involved not merely the adoption of weapons technology but also the influx of craft items with cultural and political significance.

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The Influence of Asuka-Period Technology Imports on Later Periods

Bridging to Tatara Iron Smelting

The iron-refining technology introduced from the continent during the Asuka and Nara periods would subsequently undergo transformation and development into Japan's distinctive *tatara* iron-smelting method. The characteristic feature of *tatara* is the tamahagane (jewel steel) obtained by reducing Japan's iron sand (magnetite-type) at low temperatures over extended periods.

*Tamahagane* is a heterogeneous steel ingot with areas of differing carbon content, but this very heterogeneity later gave rise to the uniquely Japanese sword-making technique of "combining outer and inner steel through repeated folding and forging." The result of "consulting continental refining techniques while developing in a different direction" was the creation of the Japanese sword——a unique sword-making culture.

Settlement of Immigrant Craftsman Communities

The blacksmiths who immigrated from Baekje and their descendants settled throughout Japan as members of the *katanahe* and *kanuchihe* guilds, serving various clan leaders and nobility while transmitting their techniques. The existence of such craftsman communities formed the production base for swords during the Nara and Heian periods, eventually creating a long chain of technical transmission leading to the golden age of the Japanese sword in the Kamakura period.

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Conclusion——The Significance of the Asuka Period's "Sword Import Era"

The Asuka period represents an era of "import and assimilation" in Japanese sword history. Under Empress Suiko's proactive foreign relations policy, the steel-refining technology, heat-treatment techniques, and sword designs flowing from Tang and Baekje significantly elevated Japanese forging technology.

Critically important is that Japan did not simply imitate these technologies but rather adapted and indigenized them to suit Japan's geographic conditions (the type of iron sand available, climate, and forest resources). It is hardly an exaggeration to say that the Asuka period's "capacity to learn" became the foundation for the later creation of "the Japanese sword——a sword-making culture without equal in the world."