300px|thumb|Walls of [[Shuri Castle]]
In the Ryukyu Islands, are castles and fortresses that feature stone walls. The origin of remain controversial. The Gusuku period of the islands is the archaeological period in which most are thought to have been built; it follows the shell-mound period and precedes the Sanzan period. Many and related cultural remains on Okinawa Island have been listed by UNESCO as World Heritage Sites under the title Gusuku Sites and Related Properties of the Kingdom of Ryukyu.
Philological analysis
The Yarazamori Gusuku Inscription (1554) contains phrases, "pile " (くすくつませ) and "pile up and ..." (くすくつみつけて); apparently, in these phrases refers to stone walls. In the Omoro Sōshi (16th–17th centuries), the term is written as "くすく," or "ぐすく" in hiragana. Occasionally, the Chinese character "城" (castle) is assigned to it. In later ryūka and kumi odori, the reading shiro is also used for the same Chinese character, in addition to also using 城内 (shiro-uchi; inside the castle). The references to in the Omoro Sōshi are mostly about castles and fortresses, but sacred places and places of worship are called as well. In some cases, simply refers to Shuri Castle. The Liuqiu-guan yiyu (琉球館訳語), a Okinawan dictionary written in Chinese, maps Chinese "皇城" (imperial palace) to the transcription "姑速姑" (gu-su-gu). Similarly, the Yiyu yinshi (音韻字海) assigns "窟宿孤" (ku-su-gu) to "皇城." Similarly, Higashionna Kanjun raised doubts over the analysis of gu since older records always used honorific u (< o) instead of gu (< go). Nakahara Zenchū identified gu as go (stone). Examples of each are Nakagusuku Castle, Nakijin Castle, Zakimi Castle, and parts of Shuri Castle. The shape of walls usually follows the contours of the land. They are usually thick, and sometimes have low parapets atop them. Some walls, like those of Nakagusuku Castle, were designed to resist cannon fire.
Bailey
have one or more baileys. The baileys of typical usually contained a residence, a well, an , and storage buildings. Larger , like Nakijin Castle, could have more than five baileys, while smaller , like Iha Castle, had a single bailey.
Gates
have one or more entrances, often guarded by a heavy gate or gatehouse. Gates were the strongpoints of . Many , like Nakijin Castle, were adapted to have gun ports next to their gates.
Main Hall
At the heart of most was the . The Main Hall was typically the residence of a feudal lord (). The palace at Shuri Castle is the most prominent Main Hall, being the only one remaining, but the site of the Main Hall is very obvious at other , such as Katsuren Castle.
Utaki
Almost all contain or are near an (), shrines and sites of religious importance in the Ryukyuan religion. The relationship between and has led some experts to question the origin and essence of .
Research
Okinawa Islands
Although it is widely recognized within the Okinawa Islands that are castles/fortresses, there is ample reason to question this perception. The origin and essence of were actively discussed in the 1960s and 70s and remain controversial.
Cultural geographer Nakamatsu Yashū claimed that the essence of was a sacred place. His theory was backed by decades of field work that was not limited to the Okinawa Islands but that extended to Amami, Miyako and Yaeyama. He revealed that an overwhelming majority of what were called by local communities did not look like castles or fortresses at all. In fact, they were too isolated from local communities, too small to live in and lacked water supply. Among hundreds of , only a dozen were fortifications. Each community usually had a . were typically located on hills, but some were on sand dunes, on cliff edges, and in caves. In some communities, what were called were actually stone tombs. Nakamatsu explained the great diversity of by one feature in common: sacredness. According to Nakamatsu, a was in origin a place of "aerial burial." The reason that a dozen of were transformed into fortress/castle-like structures is unclear, but he conjectured that some rulers had expanded substantially by building their family residences around them. Shuri Castle, for example, encompasses sacred places such as and , which suggests the original nature of the castle.
Archaeologists from Okinawa Prefecture have labeled some archaeological findings as . Takemoto Masahide claimed that gusuku were defensive communities. He classified what he considered into three types:
- A: residence of political leaders, a fortress/castle with stone walls,
- B: defensive community, and
- C: place of ancestor worship or burial place.
According to Takemoto, Type B, which is overwhelming in number, appeared during the transitional period between primitive society and class society. As noted by Asato Susumu, there is a significant gap in the use of the term . While Nakamatsu referred to limited space as , Takamoto applied the term to the whole archaeological site.
Archaeologist Tōma Shiichi hypothesized that a was the residence of an (local ruler or warlord) and his family. Since most in the Okinawa Islands are accompanied with stone walls, he considered that the Gusuku Period was characterized by the formation of class society. Among archaeologists, however, Kokubu Naoichi supported Nakamatsu's theory considering poor living conditions of .
While typical castle/fortress-type in the Okinawa Islands were featured by stone walls, it was discovered in the 1980s and 90s that some fortifications in northern Okinawa Island lacked stone walls but instead were characterized by earthworks, kuruwa and dry moats. This style of fortifications is in fact rather common in Amami Ōshima and representative of medieval mountain fortifications (中世山城) of Japan. Naka Shōhachirō and Chinen Isamu, a historian and an archaeologist from Okinawa dated them to the late 12th to early 13th centuries and claimed that they were predecessors of with stone walls. This view was actively criticized by Takanashi Osamu in the late 1990s and 2000s. Few sites can be attributed to the fact that the Sakishima Islands were over a hundred years behind Okinawa socially and technologically. In 1500, Ryukyu invaded and annexed the islands, which would have limited further local development. The primary site in Yaeyama is Furusutobaru Castle, residence of Oyake Akahachi, which was attacked by Nakasone Toyomiya of Miyako shortly before the invasion by Ryukyu.
Linguist Nakamoto Masachie noted that in some dialects of Yaeyama, gusuku/gushiku means stone walls themselves (not a structure with stone walls) and conjectured that this might be the original meaning of . According to Ono Masatoshi, has various meanings, depending on dialects of Yaeyama, including a partition of a mansion and stone walls surrounding an agricultural field. The local people call these remains busu nu yashiki (bushi's mansion), (bushi's house's stone walls) or (bushi's house), (bushi's mountain) in Ishigaki, bushin yaa (bushi's house) in Hatoma, nishi nu bushi nu yaa (bushi's house in the north) in Aragusuku.
In the archaeology of Yaeyama, human settlements prior to the conquest by Ryukyu are called "Suku Villages" because the names of these ruins have the suffix -suku. By extension, the archaeological epoch of the Suku Culture (11–16th centuries) is sometimes used by archaeologists. His comprehensive study found 129 toponyms in Amami Ōshima. Similarly, a 1982 research project by Kagoshima Prefecture covered 45 fortifications in Amami.