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. Miki carefully noted that, as Nakamatsu had shown, most of what were called were not fortifications, and that conversely, some fortifications were not called by the locals. A major difference from those in the Okinawa Islands was that in Amami (except those in
Okinoerabu and
Yoron) nearly completely lacked stone walls. As a historian from Japan, Miki took much notice of the religious nature of in Amami, which is completely absent from Japanese fortresses. Publications from Amami gained attention of some Okinawan archaeologists in the 1980s and 90s, and they attempted to place Amami's in the Okinawan -as-fortifications framework. Naka Shōhachiro investigated some in Amami Ōshima and discovered
kuruwa and dry moats there. He claimed that the primary function of those was defensiveness, not religiousness as Nakamatsu claimed. He dated them to the late 12th to early 13th centuries and considered that they subsequently evolved into those with stone walls in Okinawa. By contrast, Miki conjectured that the construction of these fortifications was triggered by repeated invasion by the Ryukyu Kingdom in the 15th and 16th centuries. In his survey of earlier studies, Takanashi Osamu criticized Naka's theory because his dating lacked evidence. In fact, with established dates were mostly from the 14th to 16th centuries. While other archaeologists had focused on mountain fortifications, he paid attention to in flat land. He also indicated the possible presence of in the
Tokara Islands, which are located to the north of Amami. From 1995 to 2000, a comprehensive investigation of was conducted in
Naze (merged into the city of
Amami in 2006) of northern Amami Ōshima. This project initially relied on toponyms to find archaeological remains but discovered far more remains in the mountains than expected. Among 45 sites discovered, only five had toponyms. This suggests that these sites were not in origin and that some of them were later transformed into . The toponymic survey also found that some earlier archaeological reports had labeled even though the referents were not called by locals. As a result, so-called "Uragami Gusuku", for example, was renamed to "Uragami-Arimori site." Earlier studies pointed to the similarity between in Amami, northern Okinawa Island and medieval mountain fortifications of Japan. Takanashi went further claiming that these fortifications were indeed medieval mountain fortifications. He considered the possibility that there were gaps in time among (1) the beginning of the archaeological sites, (2) the construction of defensive structures and (3) the applications of the name of gusuku. He re-evaluated Nakamatsu's sacredness theory and presented a working hypothesis that in Amami were of secondary origin, possibly related to the introduction of the
noro priestess system by the Ryukyu Kingdom. ==List of castle/fortress-type ==