Shiwajo Castle

-From castles of nation to forts of local power (2)-

Overview

Name: Shiwajo Castle (Shiwajo)
Alias:
Place: Shimoota Morioka city, Iwate
Type: Flat Castle
Built: 803
Remaining remnants: Clay walls and dry moats
Title:

Brief History

Shiwajo castle (志波城) is located at the center of half-round flat plain spreads at the southward of Shizukuishi-gawa river and at the west of Kitakami-gawa river. Current Morioka city central spreads over the east side of Shizukuishi-gawa river and Kitakami-gawa river, then castle site is at the opposite of two rivers from Morioka city central.

Shizukuishi-gawa river which flows from Ou mountains toward east is used as a communication route toward Yokote basin and Akita basin of current Akita prefecture across the mountains. Beside, abundant melt water wet the fields of the area, but sheer slope of the ground and abundant water also was a cause of severe flood before the construction of Gosho dam.

Castle site is placed over long and narrow slight elevation spreads east and westward along with the direction of Shizukuishi-gawa river. Avoiding the effect of flood, this small elevation has been developed since ancient era, and many old tombs were built in 7th century and 8th century by local residents.

Expansion of Imperial Household into Kitakami basin

In the latter half of 8th century, the power of Imperial Household already reached to the north edge of current Miyagi prefecture from its regional base Tagajo castle (Miyagi prefecture). Further the Imperial Household tried to expand its territory into Kitakami basin, but faced strong resistance of local residents called as “Emishi” and suffered fatal defeat at the battle of Subushi in 789.

Tamuramaro Sakanoue (758-811), a talented general of the Imperial Household, at first served as the vice commander of the expedition held in 794. Later Tamuramaro was appointed as “Seii Taishogun”, a grand general of marginal area which later turned to the name of Shogun, from Emperor Kanmu (737-806) and seized the command of the army at Tohoku region.

After careful preparation for several years, in 801 Tamuramaro Sakanoue entered into Kitakami basin and broke the army of local residents. Tamuramaro once returned to Kyoto city but next year visited Kitakami basin again to build Isawajo castle (Iwate prefecture), a forefront base of Imperial Household at the south part of Kitakami basin .

Construction of Shiwajo castle

During the construction of Isawajo castle, Aterui (?-802) who was the leader of local residents and broke the Imperial Household army at the battle of Subushi surrendered. Tamuramaro Sakanoue took Aterui and his colleague Mori to Kyoto city and recommended to accept the surrender, but the cabinet declined this recommendation and executed Aterui and More.

At the same time, castle site was governed by another leader Anusiko but Anusiko followed to the Imperial Household earlier. Due to stabilization at the south part of Kitakami basin Tamuramaro Sakanoue marched northward to current Morioka city area. In 803, preparing further expansion toward the north edge of Kitakami basin, Emperor Kanmu ordered Tamuramaro to build Shiwajo castle, and Shiwajo castle might be completed at that year.

Shiwajo castle is at the same diameter as Akitajo castle (Akita prefecture), another basement of Imperial Household at the side of Sea of Japan. Both areas are north edge of plain area and worked as the north border of ancient Japan in cooperation. At the north of this line there are flat places such as Hachinohe area, Noshiro area or Tsugaru plain, but direct action were not taken to such areas.

Structure of Shiwajo castle

Basic structure of Shiwajo castle is same as Isawajo castle, which consists of square shaped outer wall and inner area. Outer wall of Shiwajo castle is about 840 meter long square, and two size larger than Isawajo castle that size is about 670 meter long square. Outer wall is built by pressed clay and was about 4.5 meter tall and 2.4 meter wide, which was same as Isawajo castle.

Outside of outer wall there was a dry moat which was about 6 meter wide and 1 meter depth wholly encircled the outer wall. About 60 meter apart, there were watching place of the guardians straddled over the top of clay wall. At the middle of south line, were was a main gate of the castle which was a two story barrack gate of 20 meter width, which is equivalent to the south gate of Isawajo castle.

Inner area is about 150 meter long square area and larger than that of Isawajo castle which was 90 meter long square, and even Tagajo castle that was 120 meter long and 100 meter width and the main place of vice capital of ancient Japan. Inner area had four gates at the middle of each line, but the south gate was a main gate and held a hiding fence at the backside of the gate.

Isawajo castle had one main hall and several barracks, but Shiwajo castle held one main hall and two sub halls, and about 10 barracks in the area. The structure of inner area looks like the one of Tagajo castle or Dazaifu city which were vice capitals of ancient Japan, and the Imperial Household might think Shiwajo castle was equivalent to such castles and substitute the function of Tagajo castle.

Surrounding inner area, remnants of barrack building were found and they might be administrative buildings. At the south of these buildings there were halls to be used for shacks and there might be blacksmiths. Near the outer wall there might be over 1,000 shacks with stove, and they might be a camp of guardians sent to Shiwajo castle.

Abolition from policy change

Being appraised for the stabilization of Kitakami basin and build of Isawajo castle and Shiwajo castle, Tamuramaro Sakanoue promoted to “Sangi”, the member of cabinet. Tamuramaro was appointed as “Seii-Taishogun” again in 804 and prepared for next expedition, but in 805 Emperor Kanmu decided the resume of expedition and construction considering fiscal problem and exhaustion of people.

In 811, Watamaro Funya (765-823) who worked under Tamuramaro Sakanoue made last campaign at Kitakami basin and fixture whole part of Kitakami basin. Watamaro reported the closure of expedition and declined of troops to the Imperial Household, then this policy was accepted.

As Shiwajo castle was too large and needs preservations costs, Tokutanjo castle (Iwate prefecture) which was about half size of Shiwajo castle was built at backside. Shiwajo castle was abolished and materials were reused for the construction of Tokutanjo castle. For a while a troop stayed at the ruin of Shiwajo castle but retreated, then Shiwajo castle went back to waste land and its north part was broken by the flood of Shizukuishi-gawa river.

Afterward of castle

The ruin of Shiwajo castle was covered by soils and slightly remained outer clay wall was seemed as the military camp of Minamoto clan at the battle of Zenkunen in 11th century. But at the construction of Tohoku Jidoshado Expressway the ruin was found by excavation and specified as the ruin of Shiwajo castle recorded in the history.

All building was lost, but now south gate and outer fences at both side of the gate, fence of inner area and three gates except for north side were reconstructed. As the historical museum park, it shows the shape of magnificent castle of 1,200 years ago, especially for the main street between the south gate of outer area and main gate of inner area.

Huge and thick clay wall built at flat land is different from other Japanese castles and looks like a western or mandarin one. It shows Shiwajo castle was a product of national project, thus it might not be built without strong support of nation and it had to disappear after the policy change of the central government.