Gusuku period

The Gusuku period (グスク時代, Gusuku jidai) is an era of the history of the Ryukyu Islands corresponding 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. Directly following the Shellmidden period, the Gusuku is generally described as beginning in the 11th century, following a dramatic social and economic shift over the previous centuries. The Shellmidden-Gusuku transition has been linked to Japonic-speaking migrants and influence from the Dazaifu trade outpost on Kikaijima, leading to the emergence of the Proto-Ryukyuan language.

The period saw extensive agriculture in 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 of sulfur and turbo snail shells. A unique vernacular architecture emerged in the region, featuring elevated village houses, initially defended by palisades. The rise of the local aji nobility steadily led to the expansion of fortifications, eventually leading to the construction of the namesake gusuku. These developed into massive stone fortresses which proliferated across the archipelago, especially on Okinawa and Amami.

By the 14th century, three kingdoms (the Sanzan) emerged as tributary kingdoms; these may have been confederations of aji, or simply prestige labels which aji operated under in the Chinese tribute system. In 1429, Shō Hashi emerged as the sole tribute king of Okinawa, although he likely failed to achieve political hegemony over the island. After a series of short-reigning kings, warfare, and succession disputes, Shō Shin conquered much of the Ryukyu Islands and organized a centralized kingdom at Shuri gusuku, ending the Gusuku period and ushering in the Ryukyu Kingdom.