Iwaya castle ruins-Shimazu and Toyotomi samurai battles. Fukuoka, Kyushu.

Iwaya castle ruins sits within Onojo fortress ruins.  Onojo fortress dates back to the 7th century making it probably the oldest fortification in Japan.  Iwaya castle dates back to the 16th century.  Finding information about Iwaya castle has been virtually impossible.  I searched both Japanese and English.  However, I must say on thing that really impressed me.  Visiting Iwaya puts into perspective how huge the Onojo fortress ruins are, even though they are nearly 1000 years older.  The Iwaya castle ruins sit inside the Onojo fortifications, although Iwaya castle, from what I can see was quite small.  Anyway, until I can get more info about Iwaya, I’d like to share an account of the Iwaya castle seige I found on the Samurai Archives website, so these are not my words.

The 1586 siege of Iwaya castle was a battle which took place as part of Shimazu clan efforts to take control of all of Kyushu.

With the defeat of the Ryûzôji clan at Okita-nawate in 1584, the Shimazu returned their full attention to their push into Ôtomo clan territory. Iwaya was located in Daizaifu, in the south of Chikuzen province, and was controlled by one of the pillars of the Ôtomo house, Takahashi Shigetane (Jôun) and his son Tachibana Muneshige, with a force of some 760 men. Jôun rejected the Shimazu calls for their capitulation, believing that reinforcements from Toyotomi Hideyoshi and the Môri clan would arrive soon.

After holding out for two weeks against enormous odds, Shigetane, aware of the futility of further resistance, committed suicide. When the Shimazu heard of his end, they are said to have prayed for his spirit, so impressed were they by his bravery. In the end, the defenders of the castle were destroyed entirely; however, the attackers suffered considerable losses as well. Hesitant to get involved in a lengthy engagement, the Shimazu then left it up to their newly acquired retainers of northern Kyushu to besiege Muneshige’s Tachibana castle for him.

This siege caused the Shimazu invasion of Bungo province to be delayed; Toyotomi Hideyoshi would arrive the following year and seize Kyushu for himself before the Shimazu were able to complete their own conquest of the island. End.


Notes.  So actually for me, this account of the Iwaya battle also shows what else is happening in Kyushu at the time.   We can see that the Shimazu from down south has just about full control of all the regions of Kyushu.  In the past the Otomo clan were quite a powerful family but after their early problems with the Mori it seems to have left them weak and dependent on the Mori and Toyotomi.  The Shimazu allied with the Akizuki clan who were the local damiyo in Fukuoka but eventually they were defeated by the much stronger Toyotomi army who had support from the Mori of Hiroshima.  Very interesting.

Text from Samurai Archives, photos by Stuart.


  1. Domo Arigato for posting. 🙏🏻🇯🇵💕 I am based in UK and have visited Nippon twice. I am currently writing a Trilogy based in Medieval Japan. If you wish to chat.


    1. Thankyou for taking the time to read the article. Please scroll through and feel free to read some others. I also have a large range of book and academic journals referenced. Good luck with the trilogy. I look forward to reading it.


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