Ryūkyū Kingdom was an independent kingdom, it had ruled most of the Ryukyu Islands from the 15th century all the way to the 19th century. The kings of the Ryūkyū Kingdom had unified all of Okinawa Island and had extended their kingdom to the Amami Islands in modern-day Kagoshima Prefecture, and the Sakishima Islands near Taiwan. Although the Ryūkyū Kingdom was small, it had played a central role in the maritime trade networks of medieval East and Southeast Asia.
Sometime in the 14th century, small domains that were scattered on Okinawa Island were unified into three parts which; Hokuzan (Northern Mountain), Chūzan (Central Mountain), and Nanzan (Southern Mountain). And these three principalities became known as the Sanzan (Three Mountains), or The Three Kingdoms period. Hokuzan was the largest area of the island, as well as holding much military power, it held the northern half of the island, though it was the weakest in terms of economically.
Nanzan was at the southern portion of the island, and Chūzan was laying in the center, and was the strongest in terms of economical ideals.