Gassan Toda Castle




The original castle here was built around the end of the Heian Period or early Kamakura Period, but it is not known exactly when or by whom a castle first constructed on this site. It was the home of the Amago clan during the end of the Sengoku Period until they were conquered by Mori Motonari in 1565. In 1600, Horio Yoshiharu moved into the castle and rebuilt and fortified the castle. Horio decided that that Gassan area was not conducive to developing a thriving economy so he started work on Matsue Castle. Gassan Toda Castle was abandoned in 1611 when Horio moved to Matsue.

Visit Notes

There are very few buses form Yasugi Station so the round trip can result in a lot of waiting. The person at the Tourism Information Desk recommended I take a taxi. This was good because I was able to have some time to see Yonago Castle afterwards. The Honmaru is at the top of the mountain behind the building in the picture above and well worth the hike.

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  • stone walls of the otemon
  • horikiri
  • horikiri moat
  • Inside the reconstructed building
  • Some stone walls of the Sanchu Palace area
  • Stone walls of the Sanchuu Palace area
  • Some of the stone walls of the Sanchuu Palace.
  • Some of the stone walls from a gate of the Sanchuu Palace.
  • stone walls around the Sanchuu Palace Area
  • Sanchuu Palace area
  • Stone walls of the Sannomaru Bailey
  • moat between the Ninomaru and Honmaru baileys
  • The Ninomaru as taken from the Honmaru bailey
  • Honmaru bailey
  • Stone walls of the Sannomaru Bailey
  • stone wall of the Sanchuu Goten
  • map

Castle Profile
English Name Gassan Toda Castle
Japanese Name 月山富田城
Alternate Names Gassan-jo, Toda-jo
Founder unknown
Year Founded 1600
Castle Type Mountaintop
Castle Condition No main keep but other buildings
Designations Top 100 Castles, Top 100 Mountaintop Castles, National Historic Site
Historical Period Pre Edo Period
Features trenches, stone walls
Visitor Information
Access 3000 yen taxi or very infrequent bus (Yellow Bus) from Yasugi Sta.
Visitor Information
Time Required
Location Yasugi, Shimane Prefecture
Coordinates 35° 21' 38.88" N, 133° 11' 7.55" E
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Added to Jcastle 2011
Contributor Eric
Admin Year Visited 2010
Admin Visits November 19, 2010

(4 votes)
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39 months ago
Score 0++
Updated to yellow; has reconstructed buildings on site.


41 months ago
Score 2++

Gassan-Todajō (Yasugi)  月山富田城 [安来]

Gassan-Todajō is a huge yamajiro (mountaintop castle) ruin. It can be broadly split into the lower and upper ruins. The lower ruins consist of series of baileys and terraced slopes either side of the main path to the castle, as well as, at the top of the path, the ruins of the "Middle Mountain Palace", which has the most extensive ishigaki (stone-piled ramparts) to be found at the site. I came to this area first. From here I could see a large segment of dorui (earth-piled ramparts) in one of the baileys off to the right. Of the baileys leading down to "the ground" on the left, I followed these on my way back to the carpark, and they include some reconstructed castle buildings in one bailey, and some ishigaki lining others. I basically stuck to the well-trodden paths on this one but even so I could see other baileys spreading out toward the plain. And from the car park one can see baileys to the right leading up the mountain, and, like islands of elevation at the fringe of the valley plain, two more baileys on the left, one of which is now a necropolis. If one goes between these ravines of shorn earth, one comes to Jōanji ("Castle Harmony Temple"), which also has impressive ishigaki. Above that temple is a whole other section of mountain which was carved into fortifications, but I did not have time for this half of the castle ruin.

From the castle's mid-section I took the switchback trail at a trot up to the castle-mount's summit, which contains the castle's most integral baileys: honmaru (main bailey), ninomaru (second bailey) and sannomaru (third bailey). The second and third baileys are not only clad in ishigaki, but also half-ringed by a belt bailey which allows us to better appreciate the ishigaki from directly below, and some of the upper castle's most engaging spots are here. Taking the path to the honmaru first, I came by lots of ishigaki that was hard to see because of the lush summer growth of vegetation. A large trench separates the honmaru from the others, and there is a small shrine located at the back of it. The "far side" of the castle, eventually leading to the temple Jōanji, can be presumably be accessed from this point too, but this route probably isn't recommended in summer. The views from the sannomaru of the rest of the castle ruins and the plain below are really incredible.


The origins of Gassan-Todajō are obscure but from 1396 it was controlled by the Amago Clan. Between 1542 and 1543 castellan Amago Haruhisa repelled a siege by Ôuchi Yoshitaka. The siege was the pivotal moment in a long series of conflicts which had become increasingly desperate for the Amago Clan, and proved to be a complete turn-about for them. From 1522 the Amago and Ôuchi Clans had contested Aki Province, and the Amago were eventually defeated completely there in 1541. The next year Ôuchi Yoshitaka invaded Izumo Province in a coalition with Mōri Motonari, heading for Gassan-Todajō. However, Kikkawa Okitsune betrayed the coalition, severing their supply lines. Although the siege was drawn out, it ended in a disastrous retreat for the attackers. The Ôuchi Clan was severely weakened and eventually succombed to internal strife, culminating in a coup known as the Taineiji Incident in which Ôuchi Yoshitaka was deposed by his chief retainer, Sue Harukata.

After changing the fortunes of the Amago Clan, Gassan-Todajō had gotten a reputation as an impregnable castle which could withstand any siege. This proved true, but only until 1566 when, after a lengthy siege, the castle finally fell to Mōri Motonari. The fall of the castle, however, was arguably down to Amago Yoshihisa's poor command, as, suspecting his commander, Moriyama Hisakane, of betrayal, he had him executed, and this led to mass desertions of his troops. Yoshihisa then surrendered and took the tonsure. With the fall of Gassan-Todajō, Mōri Motonari had defeated his two initially more poweful rivals, the Ôuchi and the Amago, and lorded over eight provinces in the Chūgoku region, although a rebellious remnant of the Amago led by Amago Katsuhisa fought on.

From 1567 the castellan of Gassan-Todajō was Amano Takashige. As mentioned, the Amago were still rebelling and in 1569 the castle was assaulted by their former vassal, Yamanaka Yukimori, but held. That year Mōri Motoaki took over command of Todajō. From 1585 Suesugu Motoyasu took over, having participated in the invasion of Shikoku under Toyotomi Hideyoshi. From 1591, Kikkawa Motoharu, Mōri Motonari's son and renowned warrior, became castellan of Todajō.

After the climatic battle of Sekigahara, many lands changed hands as the victors were awarded the territories of the defeated. This was an important transitional period from warring states to (relatively) peaceful Tokugawa hegemony. Many castles inherited by Tokugawa supporters in their new feifdoms proved inconvenient and poorly located for the new priority of developing a strong economic base around castle towns. Gassan-Todajō was such a castle. Horio Yoshiharu was enfeoffed with the territory but found the Todajō ill-suited to his needs, and so he built Matsuejō instead. Many Edo Period castles have a Sengoku Period antecedent, and Matsuejō's is Gassan-Todajō. From 1600 Horio Yoshiharu was lord of Gassan-Todajō; in 1611 the castle was decommissioned.