often refers to castles or fortresses in the Ryukyu Islands that feature stone walls. However, the origin and essence of gusuku remain controversial. In the archaeology of Okinawa Prefecture, the Gusuku period refers to an archaeological epoch of the Okinawa Islands that follows the shell-mound period and precedes the Sanzan period, when most gusuku are thought to have been built. Many gusuku 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 gusuku" (くすくつませ) and "pile up gusuku and ..." (くすくつみつけて); apparently, gusuku in these phrases refers to stone walls. In the Omoro Sōshi (16th–17th centuries), the term gusuku 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. The references to gusuku in the Omoro Sōshi are mostly about castles and fortresses, but sacred places and places of worship are called gusuku as well. In some cases, gusuku simply refers to Shuri Castle. The Liuqiu-guan yiyu, a Chinese dictionary, maps Chinese "皇城" (imperial palace) to the transcription "姑速姑" (gu-su-gu). Similarly, the Yiyu yinshi assigns "窟宿孤" (ku-su-gu) to "皇城."
Etymology
There is no consensus about the etymology of gusuku. Chamberlain analyzed the word as the combination of gu (< honorific go 御) and shuku (宿). Kanazawa Shōzaburō also segmented gusuku into gu and suku but considered that the latter half was cognate with Old Japanese shiki, in which ki was a loan from Old Korean. Iha Fuyū proposed that suku was cognate with soko (塞, fortress). Hirata Tsugumasa considered that suku was cognate with Japanese soko (底, bottom). 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).
Common features
Walls
The most prominent feature of most gusuku is their wall(s). Gusuku walls are primarily made with Ryukyuan limestone and, sometimes, coral. There are three types of gusuku walls: aikata-zumi, nozura-zumi, and nuno-zumi. Examples of each are Nakagusuku Castle, Nakijin Castle, Zakimi Castle, and parts of Shuri Castle. The shape of gusuku walls usually follows the contours of the land. They are usually thick, and sometimes have low parapets atop them. Some gusuku walls, like those of Nakagusuku Castle, were designed to resist cannon fire.
Bailey
Gusuku have one or more baileys. The baileys of typical gusuku usually contained a residence, a well, an utaki, and storage buildings. Larger gusuku, like Nakijin Castle, could have more than five baileys, while smaller gusuku, like Iha Castle, had a single bailey.
Gates
Gusuku have one or more entrances, often guarded by a heavy gate or gatehouse. Gates were the strongpoints of gusuku. Many gusuku, like Nakijin Castle, were adapted to have gun ports next to their gates.
Main Hall
At the heart of most gusuku was the . The Main Hall was typically the residence of a feudal lord (Aji). 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 gusuku, such as Katsuren Castle.
Utaki
Almost all gusuku contain or are near an , shrines and sites of religious importance in the Ryukyuan religion. The relationship between utaki and gusuku has led some experts to question the origin and essence of gusuku.
Research
Okinawa Islands
Although it is widely recognized within the Okinawa Islands that gusuku are castles/fortresses, there is ample reason to question this perception. The origin and essence of gusuku were actively discussed in the 1960s and 70s and remain controversial.