Around 300 years before construction on Matsue Castle started, a nearby mountain was chosen as the highly defensible spot for a castle that would see its share of battle: Gassan Toda Castle, on Mt. Gassan in modern day Yasugi.

Originally built by the Sasaki clan in the 14th century in the Kamakura era, it is more commonly associated with the Amago clan, which stemmed from the Sasaki clan. This branch of the family started when Sasaki Takahisa, orphaned at the age of 3, was raised by a nun. In respect for her, he used the name Amago (尼子), which means “child of a nun.”

When you hear the term “Amago clan” (aka Amako clan), it is usually paired with the term “Mori clan.” In the Sengoku (Warring States) period of Japanese history, stated as spanning 1467~1573. There were plenty of battles before and after this period, but this is when Japan was split up amongst several warlords as opposed to power being split between only a few factions. The development was not sudden–many of the clan rivalries were based off of previous loyalities and rivalries leading up to that point, and power was gradually consolidated as clans began pledging allegiance to the more prominent warlords, and these prominent warlords gained the territories that previously been long fought over. Here in the San’in region as well as in other parts of western Japan, the Amago and Mori clans had a long and colorful history of going head to head against each other out here, but many other clans were involved as well, including the clans these clans served, or the clans that served these clans. (Still with me? Good.)

One such servant of the Amago clan was Yamanaka Yukimori, aka Yamanaka Shikanosuke (1545~1578), a famous general loyal to Amago Katsuhisa (1553~1578). He’s a celebrated local hero here in the Izumo region, especially in Yasugi, where there are big campaigns for having one of NHK’s annual Taiga drama based on his life.

The fact that he and his master have the same year of death might have tipped you off that they met a tragic end. Indeed, in was their misfortune to have been active towards the decline of the clan. After Katsuhisa’s father and brother were killed by an internal scuffle and the Mori clan effectively defeated the clan, he abandoned his monkly ways to fight, but was defeated and sought refuge on the Oki Islands. Upon his return, he captured a couple provinces, including what is now eastern Tottori. As the continued their battles with their limited armies, Shikanosuke sought an alliance with Oda Nobunaga, only to find that had only been used and no one came to their aid.

In the end, he and Katsuhisa were defeated by the Mori clan. Katsuhisa was forced to commit ritual suicide there, while Shikanosuke surrendered, but was supposedly captured and killed shortly afterward by the Mori clan anyway. As for surrending instead of following his master in suicide, some say that he sold Katsuhisa out as part of his offer to surrender, and others say that Katsuhisa willingly went along with this plan in an effort to save their remaining men. Whether they displayed cowardice or bravery in defeat, we can at least bet that a Taiga drama would build up an appropriate amount of drama around the end of an otherwise very heroic character.

With the fall of the Amago clan Gassan Toda Castle soon fell to the Mori clan as well, though it had proved to have strong defense until that point. Amago Haruhisa, the leader of the clan, successfully withheld a seige by the Ouchi clan in 1542~1543. It was a major defeat for the Ouchi clan which lead to internal struggles, and the Ouchi clan wound up being wiped out by the Mori clan later. Haruhisa went on to control territories like modern day eastern Shimane, western Tottori and the Oki Islands, but remember how Katsuhisa’s father and brother were killed? That was Haruhisa’s fault.

The Amago clan was wiped out, and although the Mori clan continued to thrive, they were on the losing side of the Battle of Sekigahara and lost control of their territory in the San’in region (but they remained in the San’yo region).

Enter the Horio clan! Horio Yoshiharu, who was with the winning side, was granted control of the Izumo domain. He moved into Gassan Toda Castle, and although it was in a highly defensible location, it wasn’t in a good spot for raising a bustling economy around it. Thus, they decided to build a new castle in a better location, and Matsue Castle was completed four years later in 1611. Matsue Castle remains one of the 12 last original castles of Japan, but Gassan Toda was not only abandoned, but pieces of it were dismantled and used in the construction of Matsue Castle.


You can, however, still climb Mt. Gassan and see what remains of the castle walls. It has been left fairly quiet, and while there is no longer a castle at the top, there is a little shrine to Ookuninushi (the same god as at Izumo Taisha) at the 197 meter summit. That seems to be a little abandoned though, too…



That said, I tend to really like the allure of things you just happen to stumble upon in the forests.




It’s a quite, peaceful mountain, and Horio Yoshiharu–who died months before the completition of Matsue Castle–was buried in Iwakuraji Temple at the foot of the mountain. However historically inaccurate, the city of Matsue still honors their founder by recreating his march into (what would become) the town and on into the castle keep with the annual Musha Gyoretsu Warrior Parade.

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While I don’t suggest taking quite that deep of a rest, you can rest up after the short hike up the mountain by visiting Hirose Onsen at the Toda Gassou facility for a nice view of the town. It’s a surphulric onsen–rich in radium-sodium, calcium chloride, and sulfide–and acts as a natural toner that gives your skin elasticity.

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I can attest to the nice view and smooth skin afterward! I wonder if the Amago clan and the warriors who served them ever had many chances to enjoy the Hirose waters?

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