If we wish to understand the history of Japanese swords, we must first familiarize ourselves with the Ancient Sword Period.It is generally believed that the Japanese sword as we know it today evolved largely from the Tang dynasty swords of China. During the reign of Emperor Kōtoku, Japan carried out the Taika Reforms, a major effort to adopt Chinese political systems, technology, and culture.
When Japan sent official missions to Tang China, the delegations included not only government officials but also many specialists. Nearly half of the members were recorded as “archers,” who in reality served as armed guards for the mission—essentially early samurai. The delegations also included blacksmiths and metal casters.
After arriving in China, these craftsmen and warriors learned extensively within their respective fields and later brought this knowledge back to Japan.
A famous example is the large sword carried by Prince Shōtoku, known as the Seven-Star Sword (Shichiseiken) or Heishi Shōrin Sword. It was forged in China during the Sui dynasty and is now preserved at Shitennō-ji Temple in Osaka.
Tang Swords in Early Japan
Japan’s Shōsō-in Repository still preserves a number of ancient Chinese swords. Historical records such as the Tōdaiji Kenmotsuchō (Inventory of Offerings to Tōdai-ji) include entries such as:
- “Tang Great Sword” (唐大刀) – referring to swords imported directly from Tang China
- “Tang-style Great Sword” (唐様大刀) – referring to Japanese reproductions modeled after Tang originals
According to the Chinese historical text Tang Liudian, there were four official types of swords during the Tang dynasty:
- Yi Dao (Ceremonial Sword)
- Zhang Dao (Guard Sword)
- Heng Dao (Side Sword)
- Mo Dao (Long Two-Handed Sword)
Modern scholars often believe that the Japanese Tang Great Sword corresponds to the Heng Dao. However, the Tōdaiji Kenmotsuchō also records a “black-forged warabi-handed heng dao,” and physical examples exist that support this description.
At the time, educated Japanese widely studied the Chinese language, so confusion in weapon terminology would have been unlikely. For this reason, the heng dao preserved in Japan was most likely the same type used in Tang China.
Interestingly, the Japanese version tends to be shorter than the Tang Great Sword, suggesting that the latter may have had a different origin or function.
One notable artifact preserved in the Shōsō-in is the gold-and-silver inlaid Tang Great Sword, decorated in an extremely elaborate style. Because of its luxurious ornamentation, it was probably not intended for combat, and is more likely comparable to the ceremonial Yi Dao of the Tang dynasty.
Characteristics of the Ancient Sword Period
The defining feature of this early stage of Japanese sword development is the straight blade.
During this period, Japan was actively learning and absorbing Chinese sword-making technology, and the distinct style of the later Japanese sword had not yet fully formed. However, several important metallurgical techniques were already well developed, including:
- Folded forging of steel
- Differential hardening and edge tempering
These techniques would later become essential characteristics of the Japanese sword.
The Transitional Sword: Kogarasu-maru
A surviving example that represents this transitional stage is the famous sword Kogarasu-maru, said to have been carried by the Taira clan during the Genpei War.
Traditionally attributed to the legendary swordsmith Amakuni, often called the “ancestor of Japanese swordsmiths,” the Kogarasu-maru reflects a transitional form between the Chinese-influenced Tang sword and the emerging style of the Japanese sword.
The blade design shows how Japanese craftsmen gradually began to develop their own identity in swordmaking while still building upon Tang dynasty foundations.
The Meaning Behind the Name “Kogarasu-maru”
The name “Kogarasu-maru” (Little Crow) may also hint at an intriguing historical connection. In the Three Kingdoms period of China, a northeastern tribal group known as the Wuhuan (also written Wuwan) was eventually defeated by Cao Cao.
Because “Wuhuan” can also be pronounced “Uwan” or “Umaru” in older transcriptions, some have speculated whether the swordsmith Amakuni might have been a descendant of these displaced peoples.
While this theory remains uncertain, the name Kogarasu-maru continues to inspire historical curiosity among sword historians and enthusiasts alike.