Still not as good as my father: Nagashino Castle and Shitaragahara ~ JUL, 2026 ~

The Toyokawa River, which flows vertically through eastern Mikawa, merges with the Uregawa River before turning west and flowing into Mikawa Bay. Nagashino Castle was built at the confluence of these two rivers, and 500 soldiers defended against the fierce attack of a 15,000-strong Takeda army. The combined forces of Tokugawa Ieyasu and Oda Nobunaga, numbering 38,000, received the news and rushed to their aid, and Takeda Katsuyori chose to fight a decisive battle at Shitaragahara. History is full of "what ifs," but if Katsuyori had exercised restraint, fortified the borders, and strengthened his country's power, the Oda clan might have faced the Honnoji Incident while under pressure from the Takeda and Uesugi clans.

The flat area where the main keep once stood is probably only about 100 meters square. Looking at the rest of the layout, the size of the castle's garrison of 500 men seems plausible. The cliffs, several tens of meters high, surrounded by two rivers, made a siege difficult, and it seems the Takeda army refrained from a direct assault and intended to surround the castle with multiple forts, spending a considerable amount of time starving the enemy out.

On the other side of the cliff was a hilly area where powerful generals, including Baba Nobuharu, were stationed at Daitsuji Temple. It was a location that overlooked Nagashino Castle and allowed for easy communication with their own forts on the opposite bank of the river.

The veteran generals trained by Shingen advised Katsuyori to withdraw when the combined forces of Nobunaga and Ieyasu arrived, but he refused, and before setting out, they exchanged farewell cups of well water.

Katsuyori established his headquarters at Iōji Temple, about 1 km behind the castle. He was within a distance where he could reach Nobunaga's army in just over ten minutes by horse across the Toyokawa River. Nagashino was a strategic point that could easily divide Ieyasu's territory, as Ieyasu had already moved his main castle to Hamamatsu, as it was about 25 km from both Mikawa Bay and Lake Hamana. His objective was probably to recapture Nagashino Castle, but he must have been unable to contain his excitement at the sight of Nobunaga leading his main force right before him. 

Only two and a half years had passed since Shingen annihilated the Oda-Tokugawa allied forces at Mikatagahara. In his will, Shingen instructed that his death be kept secret for three years, but Katsuyori had captured Takatenjin Castle, which his father had failed to take, the previous year and was trying to further expand the Takeda territory. The more territory you expand, the more exponentially the area in contact with the enemy increases, and excessive expansion of the battle lines will eventually lead to exhaustion, though it's not quite Stalingrad. Driven by a strong desire to be recognized as the successor to his excellent father, and fearing that he would lose the support of his vassals and the people of the occupied territories if he did not continue to win, the young Katsuyori could not be stopped. The area is hilly and has many streams, making it difficult to imagine cavalry galloping freely across it.

Meanwhile, Nobunaga brought a large amount of lumber and construction tools and erected multiple layers of barricades to defend against the horses. It is said that 3,000 muskets were fired in three stages during the main battle, but the latest theory suggests that only about 1,000 muskets were available at most. Furthermore, it is thought that barricades were more effective than muskets in stopping the advance of the cavalry. The effective range of muskets at that time was about 100m, and cavalry could attack in a matter of seconds. Given the risk of rain during the rainy season, it is easy to understand why sturdy barricades were the main weapon. Nobunaga knew better than anyone that the only way to defeat a large army with a small force was to charge only at the enemy general, and if he prepared and set out while reading Katsuyori's psychological state, then Nobunaga was indeed no ordinary man.

After witnessing Katsuyori's retreat, Baba Nobuharu served as the rearguard and presented his head to the enemy general unscathed. The area is dotted with the graves and mounds of many famous Takeda generals, suggesting the fierce nature of the battle.

Nearby, there's an outcrop of the Median Tectonic Line (a major fault line stretching from Kanto to Kyushu), where metamorphic rocks with different origins are layered. The darker-looking rock is green crystalline schist, which is easy to process and was used in the stone walls of Tokushima Castle and Wakayama Castle. It was formed by metamorphism caused by heat and pressure about 100 million years ago, when the Japanese archipelago did not exist as part of a continental landmass. The mountainous areas of Mikawa, Shinano, and Mino are fascinating areas for geology enthusiasts. 

In the Middle Ages, the mountainous region of eastern Mikawa was ruled by local powerful families known as the Yamaga Sanposhu, consisting of the Okudaira and Suganuma clans. After the fall of the Imagawa clan, they were caught in a relentless struggle between the Tokugawa and Takeda clans to poach their members, forcing them to make choices that would determine the survival of their families. During Shingen's westward campaign, they eventually sided with the Takeda, but many later defected, leading to Katsuyori besieging Nagashino Castle. Shingen captured Noda Castle, which belonged to the Suganuma clan, and built Furumiya Castle in Tsukude, which was under the control of the Okudaira clan, preparing to advance into the western Mikawa plains. However, due to a worsening of his health, he remained at Noda Castle and later withdrew his entire army to Shinano.

Okudaira family head Sadayoshi secretly allied with Ieyasu after Shingen's death and captured Furumiya Castle. His eldest son, Nobumasa, was the castle commander who, with a small force, repelled the fierce attack of the Takeda army at Nagashino Castle. Due to his great achievements, he married Ieyasu's daughter, Kamehime, and became the founder of the Nakatsu Domain in Buzen Province, a domain with a 100,000 koku stipend, as a quasi-family member of the Tokugawa family. Fukuzawa Yukichi emerged from the Nakatsu Domain during the late Edo period.

The site of the former Miyagi Castle is now home to the Shiratori Shrine. A visit to the nearby Tsukude Historical and Folk Museum reveals that the Tsukude plateau area was once a wetland where swans and other waterfowl bred, resulting in the accumulation of a large amount of phosphorus and fertile farmland. The area is also where deposits of ash from the massive eruption that created the Aira Caldera in the southern seas of Kagoshima Prefecture (29,000 years ago) have been confirmed, indicating that it was a marshland at least during that time, and there are several Shiratori Shrines in the surrounding area.

Incidentally, the three main nutrients for plants are nitrogen, phosphorus, and potassium, and fertilizers are formulated to contain these nutrients.

After the Battle of Sekigahara, Nobumasa's fourth son was adopted by Ieyasu and took the name Matsudaira Tadaaki (of the Okudaira Matsudaira family), and was granted Kameyama Castle, where the Okudaira clan had lived since the Nanboku-cho period. This family was a daimyo family that was transferred a great many times, moving from Ise Kameyama to Settsu Osaka to Yamato Koriyama to Harima Himeji to Dewa Yamagata to Shimotsuke Utsunomiya to Mutsu Shirakawa to Dewa Yamagata to Bingo Fukuyama to Ise Kuwana to Musashi Oshi until the abolition of the feudal domains and establishment of prefectures. Thank you for your service!

While surrounded by the Takeda army, Nagashino Castle commander Okudaira Nobumasa entrusted Torii Suneemon with a message requesting reinforcements from Ieyasu. Suneemon carried out his mission by traversing rocky cliffs and jumping into the river, but was captured by the Takeda army on his return. He was ordered to tell the Nagashino Castle soldiers that "no reinforcements are coming," but instead told them "they will be here soon," and was crucified. There is a grave for Suneemon and his wife at Kansenji Temple.

On the opposite bank of the main keep stands a monument marking the place where he was crucified. Looking at the rapids below the cliff, one can imagine how difficult his mission must have been. Suneemon's son later became a retainer of the Okudaira family and then a chief retainer of the aforementioned Okudaira Matsudaira family, and his descendants lived in the Oshi Domain until the Meiji Restoration.

Daminejo Castle, the residence of the Suganuma clan, the other of the three Yamaga clans, is a mountain castle located in the mountainous area upstream of the Toyokawa River, and a memorial hall was opened there in 1994. The head of the Suganuma clan of Daminejo, Sadatada, remained on the Takeda side even after Shingen's death, and tragedies occurred such as the purging of his family members who had split off. A branch family that sided with Ieyasu survived the Edo period as hatamoto (direct retainers of the shogun), and two sets of armor donated by their descendants are displayed inside the memorial hall, showing the love that the locals and their descendants have for the area. I was drenched in sweat climbing up the mountain, but it seems that hiking while enjoying the autumn foliage would be a better option.

The Suganuma family restored the Tamamine Kannon temple near the castle in the 15th century and made it their family temple. There is also a cafe where you can enjoy soba noodles while overlooking the mountains of Okumikawa, but unfortunately it is only open on weekends and holidays.

Since we've come this far, we'll head to Horaiji Temple. As expected of a famous spot, there was a new public parking lot on the mountainside, and from there it's about a 10-minute walk to Toshogu Shrine and Horaiji Temple. The scenery is like a sumi-e (ink painting) of a sacred valley, but the volcanic rock from 14 million years ago has been eroded, leaving only the hard parts.

The nearby Toshogu Shrine was built by Iemitsu after he heard that Ieyasu's parents (Matsudaira Hirotada and Kodaiin) had secluded themselves at Horaiji Temple to pray for a worthy heir, and its main hall is designated as an Important Cultural Property.

Other famous figures who stayed at Horaiji Temple include Minamoto no Yoritomo, Takeda Shingen, Kasuga no Tsubone, and Ii Naomasa. Although it is only about 700 meters above sea level, the unique topography makes it seem quite fitting that it is said to be a mountain where phoenixes descend.

In front of the main shrine was a rest area overlooking the world below. My heart was filled with emotion as I recalled the many dramas that had unfolded there. There was a vending machine selling canned beer, and I almost reached out to buy one, but managed to stop myself at the last moment. It must be a prize for those who climbed the 1425 steps from Omotesando.