Japan Castle Explorer: Iwao Castle -Time to treason (12) fall into dead end-

Iwao Castle

-Time to treason (12) fall into dead end-

Overview

Name: Iwao castle (Iwao-jo)
Alias:
Place: Sannan-cho Tanba city, Hyogo

Location: 35.09984350469761, 134.97351005100285
Type: Mountain Castle
Built: 1516
Remaining remnants: Stone walls, clay walls and moats
Title:

Brief History

Continued from Part 11

Iwao castle (岩尾城) is located at the park of Jyayama mountain, one of 350 meter above sea level at Yamanami area at the southwest edge of current Tanba city. Jyayama mountain spread its peak into four directions like a cross, and Iwao castle is built utilizing peak and southward ridge of the mountain.

Yamanami area is a narrow valley along Kakogawa river, a large river flows north and southward along with the western border of former Tanba province (western part of Kyoto prefecture and middle eastern part of Hyogo prefecture) into Harima province (south part of Hyogo prefecture).

The origin of Kako-gawa river is just the next of Tajima province (north part of Hyogo prefecture) where was the entrance of Sanin region, and Harima province was also an entrance of Chugoku region. Castle site is an entrance of corridor between Seto-Naikai Sea and Sea of Japan side currently followed by Route 175, and also connected to eastward road toward Sasayama area.

Origin of Iwao castle

Iwao castle was built by local lord Hitoyori Wada in 1516. It is said that Wada clan was originally the local lord of Shinano province (Nagano prefecture), and moved to Yamanami area in the latter half of 15th century.

Wada clan governed this area over about 100 years, but in 1579 this castle was attacked by Mitsuhide Akechi (1528-1582), a regional commander of central ruler Nobunaga Oda (1528-1582) who already defeated major local lords of Tanba province such as Hatano clan at Yagami castle (Hyogo prefecture) or Akai clan at Kuroi castle (Hyogo prefecture). Iwao castle fell by Mitsuhide and Wada clan ruined.

Considering the geographical importance of the castle as a guard of western border of Tanba province and grasp of communication route between Sanyo region and Sanin region, Iwao castle might be reformed as a modern castle with stone walls under Mitsuhide.

Structure of Iwao castle

Iwao castle consist of hilltop area and terraces spread along with the ridge. Hilltop area was originally a long and narrow area of about 100 meter long and 30 meter width separated into north half and south half by narrow height at its center. But after the fall of Wada clan, north half of hilltop area was abandoned and only south half faces hillside area and castle town was reformed into modern castle.

At the center of south half there is a small main tower basement of 9 meter long and 6 meter wide, and two floor small tower might exist there. Central area is a 30 meter long square area surrounding main tower basement, and has folding gate at its west side.

Secondary area covers southern and western line of the central area, and has its gate at its south part and northwest corner. At the west of these core areas there are two terraces named Nishinomaru and Demaru, and main route from hillside area connects at this place.

Plan to expand Chugoku region

In 1579, when Mitsuhide wholly captured Tanba province and opened his road toward Sanin region (Sea of Japan side of Chugoku region), Hideyoshi Hashiba (1537-1598, later Hideyoshi Toyotomi), the colleague of Mitsuhide, also seized whole part of Harima province suppressing the rebellion of Bessho clan at Miki castle (Hyogo prefecture) or Araki clan of Arioka castle (Hyoto prefecture).

At that time Oda clan entered total war against Mouri clan, thus Mitsuhide might have the plan to capture Tajima province next, then march toward the territory of Mouri clan along the Sea of Japan in parallel with Hideyoshi who proceeds along with Seto-Naikai Sea.

Actually Naomasa Akai (1529-1578) which was the local lord of Kuroi castle (Hyogo prefecture) once marched to Tajima province then once captured Takeda castle (Hyogo prefecture) and Konomiyama castle (Hyogo prefecture). As Chugoku region was separated by Chugoku mountains into north and south, thus this plan was reasonable considering the geography and power of Mouri clan.

Capture of forward route by rival

However, Hideyoshi succeeded to turn Naoie Ukita (1529-1582), the warlord of Bizen province (south half of Okayama prefecture) formerly followed to Mouri clan at Sanyo region, thus Hideyoshi could turn his army toward Tajima province. Furthermore, 10 years ago Hideyoshi once intruded into Tajima province and beat Yamana clan which was the lord of the province, thus Hideyoshi had connection and pressure to the province.

In 1580, Hideyoshi again intruded into Tajima province along with his younger brother Hidenaga Hashiba (1540-1591). Yamana clan which was deprived their main base Konomiyama castle (Hyogo prefecture) moved to more secure Arikoyama castle (Hyogo prefecture), but Hideyoshi captured Arikoyama castle and other castles then wholly captured province.

By this military operation, the territory of Hideyoshi connected to Seto-Naikai sea and Sea of Japan side, at the next of the territory of Mouri clan, then there was no room for Mitsuhide to expand westward. Furthermore, Hideyoshi captured Ikuno Silver mine, which was one of two major silver mine along with Iwami silver mine of Iwami province (western half of Shimane prefecture).

Loss of contact to Chugoku region

Hideyoshi who faced against Mouri clan only by his army suffered from limited army and division into Sanin region and Sanyo region but gradually turned the situation and pushed Mouri army toward west. In the autumn of 1581 Hideyoshi encircled Tottori castle (Tottori prefecture) managed by Mouri clan and fell it, and at this time Akechi clan only participated in as reinforcement army by their fellow Hosokawa clan.

In the early spring of 1582, Nobunaga attacked Katsuyori Takeda (1546-1582) who was the warlord of Kai province (Yamanashi prefecture) utilizing turn of Kiso clan which was the local lord of Kiso area and followed to Takeda clan. Under Nobutada Oda (1555-1582, the successor of Nobunaga, Oda army ruined Takeda clan only in one month.

At this battle Mitsuhide followed to the main force of Nobunaga marched behind of Nobutada and did not fight. And after the battle, Kazumasu Takigawa (1525-1586), another important general of Nobunaga, was appointed at the regional commander of eastern Japan, and Mitsuhide could not have his new frontline.

Loss of contact to Shikoku island

Just after his return from Kai province, Nobunaga also established Shikoku Island army under his third son Nobutaka Oda (1558-1583), to defeat Motochika Chosokabe (1539-1599), the warlord of Tosa province (Kochi prefecture) expanding to other three provinces of Shikoku Island.

Originally Motochika Chosokabe communicated to Nobunaga through Mitsuhide, as the wife of Motochika was relative of Toshimitsu Saito (1534-1582), an important retainer of Mitsuhide. At first Nobunaga supported Motochika to suppress Miyoshi clan which held Shikoku island and Kinki region before the march of Nobunaga toward Kyoto city in 1567.

However, around 1580 Miyoshi clan significantly lost their power and Chosokabe clan became too strong for Nobunaga. Nobunaga ordered to Chosokabe clan to dispose his territory other than Tosa province through Mitsuhide, but this coordination did not reached to settlement thus finally Nobunaga decided to attack Chosokabe clan.

Fall into dead end

In such case ordinary the general who communicated to the opponent turned to the vanguard, but this time Nobunaga did not use Mitsuhide and appointed Nobutaka Oda as the commander against Chosokabe clan. The reason is not clear but to prevent too much expansion of Mitsuhide and improve the importance of Nobutaka.

But by this decision Mitsuhide totally lost his fame and front line to expand. Next to capture of Chugoku region and Shikoku island Nobunaga might plan to the invasion to Kyusyu island, but this might be performed by Hideyoshi Hashiba from Chugoku region and Nobutaka Oda from Shikoku island, and there was no room for Mitsuhide.

Now Mitsuhide was the commander of Kinki region, but his predecessors such as Naomasa Ban (?-1576) or Nobumori Sakuma (1528-1582) were punished being accused their failures and no necessity in the strategy. Mitsuhide made many achievements and was trusted by Nobunaga, and there was possibility to follow his predecessor. In spite of his high situation, Mitsuhide entered dead end at Oda clan.

Afterward of castle

After the fall of Mitsuhide in 1582 after his rebellion against Nobunaga, Hidekata Sano (?-?) was appointed as a lord of Iwao castle with small territory by Hideyoshi Hashiba who beat Mitsuhide at the battle of Yamazaki and became next ruler.

Hidekata was originally a head of monk soldiers at Kido castle (Shiga prefecture) and fought against Nobunaga Oda, but was defeated and once hided. Later Hidekata served to Hideyoshi and became a lord. Hidekata further reformed Iwao castle, but in 1596 Hidekata returned to his native place Omi province (Shiga prefecture) and Iwao castle was abolished then.

Now all building was lost but half broken stone walls still remain at the peak of the mountain. Height difference between hillside area and hilltop area is nearly 300 meter and it is a bit tough to climb to the castle, but it is used as a hiking course of local people and if weather is fine beautiful scenery is seen from the castle. The castle planned to see Akechi army moving west toward Mouri clan could not play such role and just stands as a ruin on the mountain.

Continue to Part 13

Access

20 minutes drive from Kita-Kinki Toyooka Jidoshado Expressway Hikami interchange. Entrance of climbing road is at the behind of Shinnenji temple of Wada town.