The Excavation of Sea Castles

Geiyo Archipelago, lying between the Seas of Hiuchi-nada and Itsuki-nada, used to be Murakami Clan’s strongholds, and their sea castles were densely located there. The studies of sea castles have progressed these years, stimulated with the outcomes of the studies of medieval castles and supported by the accumulation of excavation data of sea castles themselves. The data point out the variations of the castles’ locations and structures, reveal their features to have numerous pits on shore reefs, and show their characteristic relics with imported porcelains etc. The study of the pits on shore reefs is attracting a considerable attention these days. The pits can be found only in the 20 castles in those areas controlled by Nojima Murakami and Kurushima Murakami Clans. The pits can be divided into independent pits, column pits and rank pits. The column pits lined at right angles to the seashores at regular intervals in a single line, while the rank pits run in parallel with the seashores in a row or two. The independent pits and the column pits are supposed to have worked to support mooring posts. However, how the rank pits were used is not specified yet. The castles and fortresses with those pits are distributed along the offshore routes. The sea castles here have 3 characteristic features. First, each castle is small in size, and even main castles can be called fortresses. They had simple structures sometimes even without forts or moats which used to be popular parts with mountain castles in the Age of Provincial Wars. Second, when a small island was fortified, water supplies were secured on the opposite shore. Third, the castles might have been distributed under the consideration of the clan’s networks and sea routes. The conceptualization of the sea castle distribution will be certainly developed with the progress of the study of pirates. Recently, the site of Nojima Castle, which is supposed to be Nojima Murakami Clan’s headquarters, was excavated and researched by Imabari City Educational Board. They found remains of residences and a smithy. The discovery was reported on Asahi (the Ehime edition) and Ehime newspapers published on February 12, 2011 and on February 17, 2011 respectively. Nojima Island today is an uninhabited island about 850 meters around located in the strait between Oshima and Hakatajima Islands in Imabari City. Taizakijima Island, about 260 meters around, is located south to Nojima Island. The width of the waterway between the two islands is about 70 meters at full tide, and about 20 meters at low tide. The whole land of the both islands is Nojima Murakami Clan’s castel, and functioned as their sea castle from the latter half of the 14th Century till 16th Century, during the Period of the Northern and Southern Courts and the Age of Provincial Wars. According to Imabari City Educational Board, two remains of residences were found at South-East Keep in the south of Nojima Island, and at the Third Keep in the west of the island. In South-East Keep, more than 10 remains of pillar pits with a diameter of 40 to 50 centimeters were found about 20 centimeters underground in the area of about 8 meters long from south to north and 4 meters wide from east to west. In Third Keep, a lot of remains of pillar pits and granite foundation stones were found about 40 centimeters underground in the area of about 8 meters long from south to north and 4 meters wide from east to west. They were lined in order in a rectangle in the both cases. A remain of a smithy with a diameter of about 1 meter was found about 30 centimeters underground near Third Keep in the north-west of the island. An unglazed earthen ventilation pipe between the bellows and furnace was found, too. The pipe is with a diameter of about 10 centimeters and length of about 10 centimeters, and is called “haguchi” in Japanese. Pieces of fired scrap iron and earth were found in chunks, iron flakes scattered around in the process of forging were left. They suggest that iron weapons were made and mended in the castle. Among the foundation stones in Third Keep, many pieces of big pots of Bizen Ceramics were excavated. They can be restored into huge pots with a diameter of 50 to 60 centimeters and in the height of about 1 meter. These discoveries are causing us to change the current view of Nojima Castle. Usually, Nojikma Castle has been regarded as a fortress in rapid currents which was utilized in wartime or in an emergency only. People might have lived at Miyakubo in Oshima. It has been handed down that there used to be Miyakubo Castle or Koga-yashiki (Koga Residence) on the hills in Miyakubo. Having water supply, Miyakubo might have worked with Nojima jointly as a castle. However small Nojima Island may be, it had buildings, and many daily earthen vessels were found in the reclaimed ground in its south. Those findings suggest that people spent their daily lives in the island. Moreover, numerous unglazed earthenware small plates in the remains of main buildings, which implies that formal samurai ceremonies similar with those carried out in the castles of war lords might have also been held there. Imported ceramics and Chinese coins were reported to have been excavated in 1938. Nojima Castle can be recognized as an independent castle which functioned by itself. Additional characteristic feature is that many sea castles were placed with sea checkpoints side by side. Many main sea castles along offshore routes, such as Kaminoseki Castle in Suo, In’noshima Murakami Clan’s Mikasaki Castle in Bingo along Aki coastal route, and Nojima Murakami Clan’s Nii-Oshima Castle in Iyo along Iyo coastal route worked as sea checkpoints as well even after “prohibitions against pirates” issued in the 16th year of Tensho, or in 1588. That leads us to suppose there probably had been more sea castles with sea checkpoints affixed.