Author: Toryu

From 武神館兜龍 Bujinkan Toryu by Toryu

Tenshō Iga War (Page 193-1199) from the book Ninjutsu Sono Rekishi To Ninja by Heishichirō Okuse.

As previously noted, the Iga ninjutsu practitioners harbored deep resentment toward 織田 信長 Oda Nobunaga, viewing him as an irreconcilable enemy, primarily due to the Tenshō Iga War.

What Was the Tenshō Iga War?

Throughout the Sengoku period (1467–1615 CE), 伊賀 Iga was largely a leaderless region. Toward the end of the Sengoku period, Niki Danjō Tomoume briefly held the nominal title of lord of Iga, supported by local chieftains, but, dissatisfied with a mere titular role, he was driven out and forced to flee—a rare event in Iga’s history.

The one who set his sights on this leaderless Iga was Kitabatake Nobuo (also known as 織田 信雄 Oda Nobuo), who had been adopted into the Kitabatake family, orchestrated the murder of his adoptive father, and seized control of the family to become the lord of Ise. Nobuo was the son of Oda Nobunaga. When Nobuo became the lord of Kitabatake, Iga suddenly found itself directly bordering Oda-controlled territory.

Nobuo noticed that a sturdy mountain castle at Maruyama in Shimogōbe, Nabari District, Iga Province—originally built by his adoptive father, Kitabatake Tomonori, as a base for attacking Iga—had fallen into disrepair. He ordered his vassal, Takigawa Saburōbē, to repair and restore the castle.

Realizing that Nobuo’s actions marked the beginning of Oda Nobunaga’s invasion of Iga, the Iga local warriors (Jizamurai) gathered at Heirakuji Temple in Ueno Castle to discuss the situation. They resolved to set aside past grievances, uniting the northern and southern Iga warrior groups to resist the external threat. Consequently, the Iga forces launched a surprise attack on the nearly completed Maruyama Castle, burning it down and driving Takigawa Saburōbē back to Ise. This occurred in July 1578 CE (Tenshō 6).

The First Tenshō Iga War

Upon receiving Takigawa’s report, Nobuo was enraged and vowed revenge. The following year, in September 1579 CE (Tenshō 7), he led an army of over 8,000 from his castle at Matsugasaki toward Iga. This marked the First Iga War. Nobuo, commanding a large army, aimed to conquer Iga in one swift campaign, splitting his forces into three routes. However, the Iga army (a coalition of local warriors), having received prior intelligence of this plan, skillfully used the mountainous terrain to block Nobuo’s advance.

From the morning to the afternoon of September 17, the Iga forces, with all ninjutsu practitioners mobilized, pinned down Nobuo’s army on the mountain paths. At night, they employed their signature night raids and surprise attacks, striking Nobuo’s forces. As a result, all three routes of Nobuo’s army suffered heavy losses, and by the morning of September 18, Nobuo himself was forced to flee for his life with his remaining troops. The outnumbered Iga army had triumphed over Nobuo’s large force.

When Nobunaga heard of Nobuo’s defeat, he reprimanded him, saying, “What a fool to cause trouble at such a critical time!” He ordered Nobuo to stand down and prohibited further military action against Iga. For Nobunaga, who was focused on unifying Japan, Nobuo’s attack on Iga was an unnecessary distraction—an example of “a child not understanding a parent’s intentions.” However, Nobunaga likely made a firm resolve at that moment: “Iga, you’ll pay for this! As soon as I have the chance, I’ll crush you completely!” His subsequent actions—the Second Iga War—reveal this intent.

The Second Iga War

Two years later, in September 1581 CE (Tenshō 9), when the tides of national power had begun to stabilize, Nobunaga suddenly gathered his generals at Azuchi Castle and ordered an immediate attack on Iga.

The announcement was so abrupt that the summoned generals were reportedly taken aback. (Nobunaga likely took great care to prevent Iga and Kōga ninjutsu practitioners from gathering intelligence, which would have given the Iga warriors time to prepare.) The invasion plan was as follows:

Iga Invasion Plan

This was an enormous army for the time. Iga’s population during this period is estimated at around 90,000, meaning the invading force was over half the region’s entire population.
Nobunaga instructed his generals to thoroughly exterminate the Iga warriors and implement a scorched-earth strategy.

On September 27, the invasion forces attacked Iga from all six routes simultaneously, descending like an avalanche. The Iga coalition army, numbering fewer than 4,000 across the entire region, stood to resist them. Despite the ninjutsu practitioners leading their得意 mountain warfare, night raids, and guerrilla tactics, the outcome was predetermined by the sheer disparity in numbers.

The battle, which began on September 27, ended after seven days with a complete victory for the Oda forces, except for a few remaining pockets of resistance. Kashiwara Castle, where southern Iga warriors made their last stand, fell on October 28, marking the end of the Iga War in both name and reality.

Excerpt above about Ninjutsu History from the book Ninjutsu Sono Rekishi To Ninja by Heishichirō Okuse.

Heishichirō Okuse (奥瀬 平七郎, おくせ へいしちろう) was a Japanese novelist, researcher, and politician born on November 13, 1911, in Ueno, Japan. He passed away on April 10, 1997.​

Okuse graduated from Waseda University and studied under the renowned author Masuji Ibuse. He developed a particular interest in ninjutsu (the art of stealth and espionage), contributing to its study and preservation. Professionally, he worked for the Manchurian Telephone & Telegraph Company.​

In addition to his literary and research endeavors, Okuse served as the mayor of Ueno from 1969 to 1977. His multifaceted career reflects a deep engagement with both traditional Japanese martial arts and public service.

The post History of Ninjutsu: Tenshō Iga War appeared first on 武神館兜龍 Bujinkan Toryu.…

From 武神館兜龍 Bujinkan Toryu by Toryu

“Differences Between Iga and Kōga” (Page 118-121) from the book Ninjutsu Sono Rekishi To Ninja by Heishichirō Okuse.

When considering the origins of the Kōga ninja clans, two key points stand out. First, 飯道山Handōzan, a Shugendō training ground founded by 役 行者 En no Gyōja, is located in the heart of the Kōga region. Second, in ancient times, the Kōga region was not distinguished from Iga and existed as part of Iga District, meaning the residents of both Iga and Kōga were essentially the same ethnic group.

The name “Iga” was established in the third year of Emperor Kōrei’s reign when the Yamato court extended its governance over both Iga and Ise provinces. According to the Nihon Shoki, “The land of Ise is the land of Isetuhiko, and Iga is the land governed by Igatuhime, ruled by their vassals,” indicating that the names used by the indigenous people were officially retained.

The original inhabitants of Iga and Ise were of the same ethnic stock, with “Iga” (IGA) meaning “mountainous interior” and “Ise” (ISE) meaning “plains,” as descriptive terms for their respective regions. After the introduction of Chinese characters, the names IGA and ISE were assigned the characters 伊賀 (Iga) and 伊勢 (Ise).

It’s unclear exactly when Kōga District was separated from Iga District, but it likely occurred sometime after the Nara period (710–794 CE). The authorities at the time chose the character 甲 (Kō), which shares the same “I” sound as 伊 (I), to name the new district Kōga.

Thus, Kōga is not a name derived from ancient phonetics but rather a repurposing of Chinese characters, meaning the term “Kōga” (KOGA) itself has no inherent meaning. Even after the separation, the cultural and ethnic unity between the two regions remained largely unchanged. Until the Tokugawa period (1603–1868 CE), when a rigid feudal system fully isolated the two, their customs, culture, and interpersonal exchanges continued as if they were still a single district.

The primary difference between the two regions lies in their political circumstances during this period. Iga was nominally under the control of temple and shrine estates (Shajiryō), so its local warriors (Jizamurai) lacked a unified military authority (Shugo, or provincial governor) to rely on. In contrast, Kōga, being part of Ōmi Province, was directly governed by the Shugo of Ōmi, a military authority connected to the central regime.

Iga’s local warriors formed a coalition government and maintained their independence, while Kōga’s warriors, whether they liked it or not, were subject to the governance of Ōmi’s Shugo.
That said, Kōga also had some temple and shrine estates, though these were limited to areas near the border with Iga District and were not significant enough to hinder the influence of the Shugo. (I even suspect that the separation of Iga and Kōga Districts may have been due to the distinction between temple/shrine estates and aristocratic estates.)

Under these circumstances, Kōga’s local warriors solidified their status as vassals (Gokenin) of the Shugo appointed by the shogunate, while maintaining strong ties with the free local warriors of Iga, navigating this era through such relationships.

It is a clear fact that these Kōga warriors learned military strategy (Heihō), which includes ninjutsu, martial arts (Bujutsu), and military science (Heigaku), at Handōzan.

Handōzan is a Shugendō training ground established earlier than Mount Hiei, making it one of the oldest Shugendō sites after Yoshino. Until Shijūkuin, a Shingon-affiliated Shugendō training ground, was established in Shijūku Village in Iga Province, Handōzan was the only Shugendō sacred site in the northern part of Iga (at the time of its founding, Kōga was likely still part of Iga District).
This training ground, which served as the foundation for transmitting the seeds of ninjutsu—Yamabushi Heihō—to Iga, was also the place where Kōga’s local chieftains trained in military strategy.

Until Shijūkuin was founded in Iga by Kūkai, the local chieftains of Iga (primarily from northern Iga) trained in military techniques alongside Kōga’s chieftains at Handōzan. It’s only natural that the Kōga warriors included a significant number of Hattori clan members, as both groups originally lived in the same region, with the Hattori being the most dominant force there. The deep blood ties between them became an invisible bond connecting the ninja clans of Kōga and Iga, a point that deserves special attention.

In any case, from the early Kamakura period, Kōga’s local warriors solidified their status by becoming vassals of the Shugo. The first Shugo of Ōmi appointed by the Kamakura Shogunate was Sasaki Sadatsuna. Sadatsuna was the eldest son of Sasaki Hideyoshi, a general loyal to Yoritomo, and the older brother of Sasaki Takatsuna, famous for his role in the Uji River battle. Their father, Hideyoshi, died in battle in Ōmi in 1184 CE (Juei 3) against Taira no Ietsugu, a Taira vassal, which likely contributed to Sadatsuna’s appointment as Shugo of Ōmi Province after the fall of the Taira clan, due to his military merits. Although there were some changes over time, the position of Shugo of Ōmi was hereditarily held by the Sasaki clan.

By the late Kamakura period, a remarkable figure named Takauji emerged in the Sasaki family, greatly expanding its influence. This Takauji, later known as Sasaki Nyūdō Dōyo after taking Buddhist vows, was a master of espionage (Yōkan). He skillfully navigated the chaotic times using the Kōga ninja groups, maintaining the Sasaki family’s status.

By this period, the Kōga ninja clans had become vassals of the Sasaki family, operating under the unified command of Sasaki Takauji. It’s likely that during this time, the foundation for what would later be known as the “Fifty-Three Families of Kōga” was steadily being established.

Can there really be two distinct schools that use the same manual, regard the same author as the foundational figure of their school, and do so without suspicion?

If we force ourselves to find a difference, it’s only that the Kōga clans are referred to as the “53 Kōga Families” and the Iga clans as the “49 Iga Schools,” reflecting the different regions where these ninjutsu practitioners resided. In other words, two regions under different administrative authorities were inhabited by the same ethnic group, speaking the same language, and practicing the same techniques—one was simply called Kōga-ryū, the other Iga-ryū. Even these regions were artificially divided in ancient times for political reasons, against natural geographical boundaries. Naturally, Iga and Kōga are essentially a single contiguous area. (Page 178).

Excerpt above about Ninjutsu History from the book Ninjutsu Sono Rekishi To Ninja by Heishichirō Okuse.

Heishichirō Okuse (奥瀬 平七郎, おくせ へいしちろう) was a Japanese novelist, researcher, and politician born on November 13, 1911, in Ueno, Japan. He passed away on April 10, 1997.​

Okuse graduated from Waseda University and studied under the renowned author Masuji Ibuse. He developed a particular interest in ninjutsu (the art of stealth and espionage), contributing to its study and preservation. Professionally, he worked for the Manchurian Telephone & Telegraph Company.​

In addition to his literary and research endeavors, Okuse served as the mayor of Ueno from 1969 to 1977. His multifaceted career reflects a deep engagement with both traditional Japanese martial arts and public service.

The post History of Ninjutsu: Iga and Kōga appeared first on 武神館兜龍 Bujinkan Toryu.…