# Gusuku period

The Gusuku period (グスク時代, Gusuku jidai) is an era in the history of the Ryukyu Islands, an island chain now part of Japan. The period corresponds to the spread of agriculture and Japonic culture from Japan alongside increased social organization, eventually leading to endemic warfare and the construction of the namesake gusuku fortresses. Following the Shellmidden Period, the Gusuku is generally described as beginning in the 11th century after a dramatic social and economic shift over the previous centuries. The Shellmidden-Gusuku transition has been linked to Japonic-speaking migrants and influence from a Japanese trade outpost on the island of Kikaijima, leading to the emergence of the Proto-Ryukyuan language, the common ancestor of the modern Ryukyuan languages.
The period saw widespread agriculture across the archipelago, including the cultivation of foxtail millet, rice, barley, and wheat. Trade occurred with China, Korea, and Japan, including imports of foreign ceramics and the export mother of pearl and sulfur. A unique form of vernacular architecture emerged in the region, featuring elevated village houses, initially defended by palisades. The rise of the local nobility steadily led to the expansion of fortifications, eventually evolving into the gusuku. The gusuku were large stone fortresses built in the hundreds across the archipelago, especially on Okinawa and Amami Ōshima.
By the 14th century, three kingdoms (the Sanzan) emerged as tributary kingdoms to the Ming dynasty of China; these may have been confederations of local nobles, or simply prestige labels under which they operated in the Chinese tribute system. In 1429, King Shō Hashi of Chūzan emerged as the sole tribute king in Okinawa, although he likely failed to achieve complete political control over the island. After a series of short-reigning kings and violent succession disputes, Shō Shin conquered much of the Ryukyu Islands and organized a centralized kingdom at Shuri Castle, ending the Gusuku Period and ushering in the Ryukyu Kingdom.

## Background

The Ryukyu Islands are an island chain on the eastern rim of the East China Sea, adjacent to Taiwan in the southwest and Kyushu to the northeast. Intermittent human settlement of the land bridge that would later become the Ryukyus began in the Late Pleistocene, around 32,000 years ago. Hunter-gatherer groups originating from neighboring Kyushu began to populate the northern and central Ryukyus around 5000 BCE, although recently-discovered sites suggest possible initial dates around 12,000–7000 BCE. This repopulation began the Shellmound or Shellmidden Period.
Complex hunter-gatherer societies emerged during the mid-Shellmidden, but polities such as chiefdoms did not emerge. This is attributed to low population sizes and the limited carrying capacity of the islands before the introduction of intensive agriculture. The Shellmidden people exploited plentiful shellfish and reef fish populations. They also hunted Ryukyu wild boar, the largest mammals on the islands, and possibly tended domestic pigs. Although other East Asian populations adopted agriculture long before the beginning of the Common Era, no cereal cultivation occured in the Ryuykus before c. 800 CE, with plant foods largely limited to nuts. Cultivation of taro or other root crops has been theorized, although without conclusive archaeological evidence. The lone unambiguously farmed crops from the Shellmidden are bottle gourd seeds recovered from the Okinawan Ireibaru site. Flotation samples by archaeologists attest a limited presence of farming from the 800s onward.
While various theories positing significant pre-Gusuku agriculture have been proposed, such developments would require the population to later abandon their dependence on agriculture before the beginning of the Gusuku period. However, cultivation remained very limited until a rapid expansion in the tenth to twelfth centuries, corresponding to a steady increase of migrants from Japan.

### Chronology

Older sources use a later definition of the Gusuku Period, beginning c. 1200 CE and stretching well into the early Ryukyu Kingdom. However, following increasing archaeological evidence for subsistence agriculture and greater social complexity in the centuries prior, 21st century sources have largely redefined the period as lasting from c. 1050 to c. 1429, corresponding to the period of increased trade, societal shifts, and endemic warfare before the centralization of the Kingdom of Chūzan and the unification of the Ryukyu Kingdom.
Within the Yaeyama Islands (or Sakishima more generally), the period corresponding to the Gusuku is sometimes labeled the Suku Period, divided between the Shinzato Mura Period (12th–13th centuries) and the Nakamori Period (13th–17th centuries). Due to their proximity and trade links to Kyushu, the Ōsumi Islands largely follow corresponding archaeological periods in Japan, adopting rice and millet cultivation during the middle Yayoi Period.

## Emergence

Beginning around 300 BCE, the Shellmidden population saw a steady decline from its peak. Populations remained low across the 1st millennium CE. The islanders traded with Japan, but saw little cultural influence from it beyond pottery designs. During the 9th century, the Dazaifu (the regional Japanese government of Kyushu) established the Gusuku site on Kikaijima as a trading outpost. Exploiting the lucrative trade of turbo sea snail shells (a source of mother of pearl highly prized by artisans), Kikaijima became a major trading hub closely tied to the Japanese port of Hakata and the Korean Goryeo; a small community of merchants from Goryeo settled on Kikaijima, leading to the creation of the Kamuiyaki stoneware with cultural influence from Korean ceramics. The Gusuku site became a polity encompassing Kikaijima and the Kasari peninsula of neighboring Amami, which was itself becoming an early center of agriculture in the region.
Beginning in the 11th century, large numbers of agrarian Japonic-speaking peoples settled the Ryukyus, with Kikaijima as the origin of various successive migration waves across the archipelago. These migrations, while all originating on Kikaijima, spread progressively southward; the Amami Islands were the first to be fully settled, followed by the Okinawa Islands, the Miyako Islands, and finally the Yaeyama Islands. This migration was likely motivated by access to various trade goods found in the southern islands, highly coveted in Song China and by the Heian aristocracy.

### Language and demography

The indigenous population of the Ryukyu Islands prior to the Gusuku migrations was of Jōmon ancestry, with little of the Yayoi genetics prevalent in mainland Japan. Interactions between this population and the Japonic newcomers varied across the archipelago. However, many Japonic communities formed cultural enclaves, evidenced by both material cultures coexisting for several centuries. In other cases, Japonic settlements emerged with practically no indigenous influence whatsoever. Indigenous culture on the islands gradually assimilated, vanishing entirely by the 14th century.
Due to their shared set of innovations absent in Japanese, the modern Ryukyuan languages are generally thought to form one of the two or three main branches of Japonic, and to descend from a common Proto-Ryukyuan origin. They retain archaic features from Proto-Japonic that were lost in Old Japanese, suggesting a divergence date no later than the 7th century. However, Sino-Japanese vocabulary borrowed from Early Middle Japanese indicates that it maintained close contact with Japanese until the 8th or 9th century. This divergence before the Gusuku Period suggests a Pre-Proto-Ryukyuan homeland in southern Kyushu and the surrounding islands. Proto-Ryukyuan itself branched off from this earlier form in the archipelago, possibly on Kikaijima, where it diversified as it spread across the archipelago.
Earlier, now-discredited, theories attribute the emergence of Proto-Ryukyuan to either the Hayato people, speakers of a divergent Japonic language, settling the Ryukyus after the conquest of southern Kyushu by the expanding Yamato state, or as an evolution from a trade creole on Kikaijima.

## Developments
### Agriculture

Large-scale cultivation as the primary means of subsistence in the Central Ryukyus began as the Shellmidden transitioned into the Gusuku. Agriculture likely took root in the Amami Islands in the 8th century, before spreading to the Okinawa Islands 100–200 years later. Rice and millet agriculture spread to Sakishima by the 12th century.
Cereal crops such as rice, barley, wheat, and foxtail millet have been found in Gusuku sites, alongside possibly beans. Southern Okinawa sites mainly grew millet and barley, while rice predominated in northern Okinawa and Amami. This rice was initially japonica rice, but tropical O. sativa was likely introduced later via trade with China and Southeast Asia. Farms were initially in low-lying alluvial regions, but gradually shifted to higher slopes. Wheat and barley were largely grown through dryfield cultivation, with irrigation largely limited to rice paddies. Cattle were used to cultivate both varieties of field. Archaeological examinations of sites at Miyako-jima have revealed similar crops to Okinawa and Amami. Foxtail millet composes the vast majority of finds, alongside smaller numbers of Adzuki beans and broomcorn millet.
The centrality of agriculture to Gusuku Period society is a topic of academic contention. Historians have generally analyzed the Gusuku as a stratified agrarian society, attributing the growth of a nobility and state polities to this agricultural base. Others have disputed this, suggesting that local agriculture was unlikely to produce a significant surplus, and instead attributing these developments to maritime trade.

### Architecture

Shellmidden-era construction was largely limited to pit-houses. The agrarian settlements of the Gusuku saw a flourishing of vernacular architecture. Settlements during the 11th to 13th centuries typically comprised several elevated main houses raised on posts with diameters of 50 centimeters (1.6 ft) or more. Pillars within the house were typically spaced by a bay (ken) of roughly 1 metre (3.3 ft), significantly smaller than the ken spacings used in traditional Japanese architecture. Houses contained hearths, with the largest having two. Elevated storehouses (termed takakura) were positioned 10–15 meters (30–50 ft) from the main structures, generally to the southwest to maximize sunlight. Some of these village sites include the remains of metalworking facilities, including pits for the storage of ironsand and hearths equipped with clay tuyeres.

#### Gusuku

In the 13th century, villages were increasingly built in defensive positions during and surrounded by palisades. By the later portion of the century, some settlements were partially encircled by stone walls. These early fortifications enclosed residential areas of both commoners and elites, as well as some utaki shrines, with satellite villages outside the walls. During the 14th and 15th centuries, these fortifications evolved into the gusuku, with the largest taking the form of massive stone fortresses enclosing elite residences, shrines, and work areas oriented around a central plaza. By the 15th century, there were approximately 100 gusuku on Okinawa, with some estimates putting the total around 200.
Stone-walled gusuku, found on Okinawa, Yoron, and Okinoerabu, were likely inspired by Korean mountain fortresses. Many were built with coral limestone, although earthen construction is attested in southern Okinawa. In the north of the island, where coral limestone was not available, ditches dug across ridges were used as fortifications. Many of the larger gusuku were built by slaves taken during pirate raids and used Japanese and Korean-style roofing tiles likely built by foreign tilesmiths who settled in the islands.
While many gusuku were permanent installations, some were occupied only during emergencies. Gusuku dramatically vary in size. Smaller structures measuring less than 2,000 m$^2$ (0.5 acres) feature a single enclosure, while much larger gusuku ranging from 1–2 hectares (2–5 acres) have multiple. Even larger fortresses exceeding 2 ha (5 acres) emerged after the end of the Gusuku period. Large amounts of military equipment, such as fragments of swords, armor, helmets, and arrowheads, have been recovered from gusuku sites. Firearms, in the form of Chinese hand cannons, were introduced to the islands during the fifteenth century. Some gusuku show damage from hand cannon fire.
Gusuku on Amami were built for mountain defense, and feature smaller enclosures and large ditches. They were built on "virtually every ridge and headland", protecting rivers and bays, often in direct line-of-sight of one another. Smaller enclosed fortifications were constructed in Sakishima, although some examples of stone-walled gusuku are attested.

### Society and governance

A class of local nobility, the aji, began to emerge during the early Gusuku period. Local aji initially constructed small gusuku as a show of political power. As particular aji consolidated holdings and absorbed the territories of neighboring lords, the fortifications steadily grew in size and complexity. The most powerful nobles were referred to as aji-osoi ("leader of lords"). They commanded local armies, and held control over less powerful aji within their territories. Larger polities shared power between the ruler and various councilors. The strongholds of powerful rulers on Okinawa were named nekuni ("root country"). Centered on gusuku, these usually had access to great wealth and resources, were able to field armies, and ruled over or pacified a wide area. The most powerful gusuku centers on Okinawa were Katsuren, Nakagusuku, Sashiki, Hanagusuku, Urasoe, and Itokazu. In Sakishima, the island of Miyako was the preeminent base of political power.

### Trade and foreign relations

Although trade links (mainly of shells) between Kyushu and the central Ryukyus date to the Yayoi, the transition into the Gusuku period saw the import of Chinese ceramics and Japanese soapstone cauldrons, used alongside native earthenware. The Gusuku people also imported iron knives and magatama from Japan. By the late 12th century, they began importing ceramics (such as Qingbai ware and celadon) directly from China, including types not found in the main Japanese islands. By the 13th century, imports shifted to Longquan celadon, with smaller amounts of Korean, Thai, and Vietnamese ceramics. In addition to the Japanese and Goryeo traders at Kikaijima, traders from the Song Empire became active in the Ryukyu Islands during the Gusuku period. Sulfur mined at Iōjima was likely exported to China via Japan.
During the late 14th century, tribute missions were sent by Okinawan aji to Ming China and Joseon Korea, with formal tribute relations with the Ming commencing in 1372; the establishment of formal tribute status during this period resulted in a much greater volume of trade. Diplomatic relationships with the Ashikaga shogunate may have been opened by the Lord of Shuri in 1403. The Ryukyus had intermittent trade connections with Southeast Asia. While merchants from Miyako and other islands in Sakishima sailed directly to Southeast Asia, rulers in Okinawa hired Chinese ships and crews to travel to the region.

#### Piracy

The Ryukyus were major bases of pirate activity from the late 13th century onward to the end of the Gusuku Period. Many of these pirates, known as wokou, were aligned with the Southern Court during the Nanboku-chō Period, with major bases on Kyushu and Tsushima. Following the collapse of the Southern Court in the 1380s and 1390s, Kyushu wokou migrated to the Ryukyus, outside of the reach of the victorious Ashikaga shogunate. Naha (on Okinawa) served as the primary port of call in the Ryukyus and became a major center of piracy and slave trading during the late Gusuku Period.

## Emergence of the Ryukyu Kingdom

Both contemporary Ming dynasty tribute records and later Ryukyuan official histories state that Okinawa was divided into three kingdoms, collectively termed the Sanzan, during the 14th and early 15th centuries: Sanhoku in the north, Chūzan in the center, and Sannan in the south. These polities may have functioned as loose confederations of aji, with their kings as confederation leaders. Alternatively, they may not have corresponded to territorial control on the island, and instead been labels that various powerful aji operated under during trade and tribute relations with the Ming.
By 1429, Okinawa's tribute relations with the Ming became the domain of a single ruler, Shō Hashi. Hashi, the son of Shō Shishō of Chūzan and possibly the grandson of a Southern Court wokou from Higo Province, came to power with the defeat of Bunei of Chūzan, likely due to the aid of Chinese officials. He was a powerful military leader, although probably lacked political control over all of Okinawa. The various other kings of Chūzan followed him as the sole tribute king of Okinawa, forming the First Shō dynasty at the Shuri Castle. After his death, the kingdom went through a rapid series of rulers of only a few years each, often marked by succession crises and wars. The kings of the First Shō dynasty may not have been linked as a bloodline or family. The southern Ryukyu Islands were under a series of local warlords, with trade relations to Shuri and the Shō dynasty.
In 1453, Shō Taikyū emerged as the ruler of Shuri. Before his death in 1460, he conquered Katsuren Castle, minted coins in his name, and took full control of trade with Korea. He launched military expeditions to Amami and Kikaijima, but failed to achieve full political hegemony over Okinawa. His son Shō Toku took the throne after his death, beginning an eight-year rule described by the Ryukyuan official histories as despotic.
A coup d'état by Shō En in 1470 founded the Second Shō dynasty. The reign of his son Shō Shin (1477–1526) saw the centralization of the Ryukyu Kingdom at Shuri and the final subjugation of outlying islands such as the Yaeyama. Local aji were forced to live at Shuri, with agents titled aji-uttchi assigned to administrate their holdings in their place. This practice destroyed the last elements of Gusuku Period local governance.

## Historiography
### Extant sources

Extremely few written documents date to the Gusuku Period, with primary sources limited to foreign diplomatic and tribute records during the latest portion of the period, such as the Ming Veritable Records and the Veritable Records of the Joseon Dynasty. A compilation of diplomatic and trade records, the Rekidai Hōan (''Precious Documents of Successive Generations''), began in 1424, around the end of the period; it was initially compiled by Chinese merchants and trade officials in Okinawa. An inscription on the Bankoku Shinryō no Kane (''Sea Bridge to the Many Countries Bell'') dates to 1458.
The first official or state history of Ryukyu, the Chūzan Seikan ("Reflections on Chūzan") was published by Shō Shōken in 1650, long after the end of the Gusuku Period, and was mainly based on interviews with elderly officials. Later state histories include the two early-18th century versions of the Chūzan Seifu ("Genealogy of Chūzan") and the mid-18th century Kyūyō (''Beautiful Ryukyu''). Largely based on Confucian historiography and principles, it is not possible to corroborate most information from the official sources dating to periods before the 16th and 17th centuries. The Omoro Sōshi is a compilation of Ryukyuan chants or songs, comprising 22 volumes and 1,553 songs, with the earliest volumes compiled during the early 1530s. Difficult to decipher and understand, the Omoro at times disagrees with the official histories. However, both are biased towards Shō Shin, the Shuri area, and Okinawa in general.

#### Traditional historiography

The official histories state that a sage king of divine ancestry, Tenson, was the first king of Okinawa, and began the 17,000–year rule of the Tenson dynasty. In 1187, Shunten, the son of the exiled samurai Minamoto no Tametomo, defeated the usurper Riyū around 1187 and began his own dynasty. A severe lack of written documentation before the 17th century limits the understanding of state and religion during the period. Shunten was almost certainly fictional, but may reflect the relocation of trading infrastructure to Okinawa after the 1188 invasion of Kikaijima. His depiction may have been inspired by the legendary Chinese Emperor Shun. Eiso is described as displacing Shunten's dynasty and ruling from 1260 to 1299. He is the earliest named ruler to appear in the Omoro. Although traditionally depicted as the king of a unified Okinawa, he was likely a regional warlord in Urasoe.

### Modern historiography

Zenchū Nakahara, writing in the 1950s, was among the first historians to identify a major discontinuity in Ryukyuan history during what would come to be known as the Gusuku Period. Highly skeptical of the official histories, he described the rise of aji, warrior culture, migrations from Japan, and endemic warfare in the twelfth century. Nakahara wrote that Shō Hashi and the First Shō Dynasty ruled Okinawa in name only and that true unification and the emergence of a mature feudal society emerged under the Second Shō. Other contemporary historians, such as Inamura Kenpu and Higa Shunchō, also identified the Gusuku as a distinct period, viewing it as a social and political transformation of an existing Japonic culture in Ryukyu analogous to Japan's earlier development.
The centrality of Japan to development in the Ryukyus was challenged in the 1980s and 1990s in favor of a mainly domestic origin, with historians such as Takara Kurayoshi and Murai Shōsuke emphasizing the independent emergence of a complex political order on Okinawa from agricultural surplus during the Gusuku Period, often placing more credence into the official histories. This in turn has been challenged by other historians who emphasize the importance of trade, with the Gusuku Period representing a sudden and dramatic break from earlier periods, as large-scale migrations of Japonic peoples early in the period led to significantly greater connections with maritime trade routes.