Thursday, March 6, 2014

Gassan Toda Castle -Rapid rise and fall of Amago clan-

Gassan Toda Castle

-Rapid rise and fall of Amago clan-



Name: Gassan Toda castle (Gassan Toda-jo/Toda Gassan-jo)
Alias: Gassan jo
Place: Hirose-cho Yasuki city, Shimane
Location: 35.36098020016571, 133.18435877567634
Type: Mountain castle
Built: Originally 12th century, expanded in 16th century
Remaining remnants: Stone walls, clay walls and dry moats
Title: 100 famous Japanese castles, Designated national historical site

Brief History

Gassan Toda castle (月山富田城) is located at Gassan mountain, one of 150 meter height from hillside just beside Hirose river 20 kilometer upstream from river mouth, in Yasuki city where resides at eastern edge of current Shimane prefecture. 

Historically this area was important for iron manufacture and shipping transportation, and was a central place of Izumo province (east half of Shimane prefecture). Gassan Toda castle was built using whole body of Gassan mountain utilizing ridges and valleys, and is regarded as one of the five largest medieval mountain castle along with Kasugayama castle (Niigata prefecture), Nanao castle (Ishikawa prefecture), Odani castle and Kannonji castle (Shiga prefecture).

Origin of Amago clan 

Amago clan which mainly used Gassan Toda castle was originally a branch house of Kyogoku clan. Kyogoku clan was also a family of Sasaki clan, originally located in the south half of Omi province (Shiga prefecture). In the late 12th century, at the battle of Minamoto clan and Taira clan, Sasaki clan rendered distinguished service under Minamoto clan, and was given the position of the governor of Izumo province and Oki province (both Shimane prefecture). 

Later Sasaki clan divided into Kyogoku clan and Rokkaku clan, then the former governed northern half of Omi province, Izumo province and Oki province, and the latter had southern half of Omi province. Around the time of the fall of Kamakura Shogunate and establishment of Muromachi Shogunate in the former half of 14th century, Doyo Sasaki (?-1373), the leader of Kyogoku clan, skillfully survived turbulent situation and became famous for his impudent behavior challenging existing authority and tradition.

In spite of his behavior, Doyo contributed to the stability of Muromachi Shogunate and appointed as the governor of Omi province which was one of the most important province for Muromachi Shogunate. Furthermore, after the temporal fall of Yamana clan which had a large territory at Sanin region, Kyogoku clan also achieved the governor of Izumo province and Oki province. As a relative of governor, Amago clan moved to Izumo province as a deputy governor. In this place there had been a castle from 12th century and Amago clan located there.

Rise of Amago clan and capture of Izumo province

Tsunehisa Amago (1458-1541), a head of Amago clan at late 15th century had excellent sense of intelligence and strong will. Ignoring his mater Kyogoku clan,Tsunehisa Amago expanded his territory to confiscate lands of temples, shrines or defiant loads. Due to a counter attack against his activity once Tsunehisa was expelled from Gassan Toda Castle by Enya clan, other powerful local lord at 1484, but he retrieved Gassan Toda castle two years later. 

According to one theory, at the new year day of 1487, Tsunehisa and his army dressed as festival dancers and sneaked into the castle, and attacked unguarded Enya clans. After the recovery of this castle, Tsunehisa forced to follow other local lords to him, and became a new leader of Izumo province instead of Kyogoku clan.

Peak of Amago clan

After 1500, Tsunehisa attempted to expand their territory to surrounding provinces. At the westward of Izumo there was also a strong lord Ouchi clan, thus Amago clan advanced toward eastern provinces between 1510 and 1540. Finally Tsunehisa held or exercised his power to provinces such as Izumo province, Oki island, Iwami province (all Shimane prefecture), Houki province (western Tottori prefecture), Bingo province (Hiroshima prefecture), Bicchu province, Bizen province, Mimasaka  province (Okayama prefecture) and even into Harima province (Hyogo prefecture).

In 1537, Haruhisa Amago (1514-1561), the grandson of Tsunehisa and successor of Amago clan, was nominated as a governor of eight counties in Chugoku region, and they became a supreme ruler in this area both in name and reality during 40 years. Tsunehisa was later said as one of three intelligent lords made social upheaval in Chugoku region (other two were Motonari Mouri (1497-1571), a warlord of Aki province (Hiroshima prefecture), and Naoie Ukita (1529-1582), a warlord of Bizen province (Okayama prefecture).

In Medieval era, Izumo province was a prosperous area because there was Mihogaseki port, which flourished by maritime trade around Sea of Japan. In addition to this, utilizing weakening of Ouchi clan occurred from the coup d'etat of their general Harukata Sue (1521-1555), Amago clan captured Iwami silver mine which now became a world heritage. Based on their political legitimacy and economic power, Amago clan became one super power in Chugoku region.

Fall of Amago clan

But in fact, Amago clan was a composite of powerful local lords and not centralized. As long as winning this issue might be no problem, but once attacked by other stronger power, not only it was impossible to perform organized counterattack, but also such local lords might forsake Amago clan considering their own benefit. In 1540 Amago clan attacked Motonari Mouri at Aki Koriyama Castle who left Amago clan, but could not capture it and faced their counter attack, then suffered severe defeat and retreated. 

Considering this defeat and the death of Tsunehisa as a good opportunity, Ouchi clan trooped to Amago clan in 1542. Once local lords of Izumo province changed to Ouchi side and Haruhisa had to besiege in Gassan Toda castle. But this castle was so secure and Ouchi clan could not occupy it for one and half year. 

Hating long campaign local lords of Izumo province changed to Amago side again, and Ouchi clan which was isolated in the enemy province was routed with serious damage. In 1554 Haruhisa purged Shinguto group, a relative house and strong army group. This was performed to strengthen the authority of the leader, but also decreased Amago’s military power.

After the extinction of Ouchi and Sue clan in 1550’s, Motonari Mouri captured their territories, and next aimed at Amago territories. Motonari was very intelligent and he persuaded to leave local loads from Amago clan by every means in advance. Isolated Amago clan was forced to stay at this castle and besieged over one year again, but considering failure of Ouchi clan, Motonari shut down all supply line to this castle and purged non obedient local retainers in advance. 

Amago clan well fought in this castle, and once they gave severe damage to Mouri army which made direct attack to this castle. But because of lack of supply, finally in 1566 Yoshihisa Amago (1540-1610), last leader of Amago clan, surrendered to Mouri clan and opened the castle. Amago clan had fallen in another 30 year from its peak.

After Amago period

In 1569, Katsuhisa Amago (1553-1578), a survived relative of Amago clan, attempted to restore the house and entered Izumo province with former Amago retainers, such as Yukimori Yamanaka (famous as Shikanosuke, 1545-1578). At first they broke Mouri army here and there, but due to lack of strategy they could not capture Gassan Toda castle, and finally ran away. This Amago restoration army kept resistance against Mouri clan, but finally ended their fate at Kouzuki castle (Hyogo prefecture) in 1578.

During Mouri period, Gassan Toda castle was governed by retainers of Mouri clan, under  Motoharu Kikkawa (1530-1586), a son of Motonari Mouri and regional commander of Sanin area. In 1591, Hiroie Kikkawa (1561-1625), a son of Motoie, was given this area independently by Toyotomi government, moved from his former main base Hinoyama castle (Hiroshima prefecture) and stayed until 1600. They modernized this castle with stone walls.

After the battle of Sekigahara at 1600, Horio clan was newly appointed as a governor of Izumo province by Edo Shogunate and transferred from Hamamatsu castle (Shizuoka prefecture). At first they located at this castle, but in 1611, they newly built Matsue castle at the lakeside of Lake Shinjiko and moved there. Gassan Toda castle was abolished since then, and the site of castle is now used as a historical park.


60 minutes bus ride from JR West Sanin-Honsen line Yasugi station to Gassan-Iriguchi bus stop. 30 minutes drive from Sanindo Expressway Yasugi interchange. 40 minutes from hillside entrance to hilltop castle.

Related Castles

Aki Koriyama Castle -Proverb of three arrows-
Hamamatsu Castle -Castle of promotion-
Matsue Castle -Old style main tower looking at water city-
Odaka Castle -Brave general devolted his life to restration of master's house-
Kannonji Castle -Strenght and weakness of Rokkaku clan-
Kasugayama Castle -Residence of "Dragon of Echigo"-
Nanao Castle -"Frost fills encampment and autumn air is purified"-
Odani Castle -History of three generations of Azai clan-
Kouzuki Castle -Castle with two tombstones-
Hinoyama Castle -Intellectual pillar of Mouri clan-


Pictures (click to enlarge)

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