The Ryūkyū Kingdom and the Shimazu clan of Satsuma have been engaged in trade for at least several centuries and possibly for far longer than that; in addition, Ryukyu at times had paid tribute to the Muromachi shogunate (1336–1573) of Japan as it has to China since 1372.

One of the chief events which spurs Satsuma to aggression had occurred when Hideyoshi launched the first of two invasions of Korea in 1592.

Through messengers from Satsuma, he had ordered that Ryukyu contribute warriors to the invasion efforts, and was refused; he had also commanded that Ryukyu temporarily suspend its official missions to China.

The mission had traveled to Beijing anyway, on business relating to Shō Nei's formal investiture, and related Hideyoshi's plans to Chinese Court officials there.

Shimazu Yoshihisa, lord of Satsuma, had then suggested that Ryukyu be allowed to supply food and other supplies instead of manpower; Hideyoshi had agreed, but Shō Nei had ignored the related missives.

Following Hideyoshi's death in 1598, and Tokugawa Ieyasu's subsequent rise to power, Shō Nei had been asked by Satsuma to formally submit to the new shogunate, a request which was also ignored.

The Shimazu now requests to launch a punitive mission against Ryukyu and, in 1606, is granted permission by the shogunate.

The invasion of Ryukyu begins in March 1609, as over one hundred ships carrying roughly three thousand warriors leave Kagoshima Harbor, under the command of Kabayama Hisataka.

After several skirmishes on the smaller, more northern islands of the Ryukyu archipelago, the fleet lands at Unten Harbor on the Motobu Peninsula of Okinawa Island.

They encounter fierce resistance there from the local peasants, and suffer considerable losses, but are ultimately victorious and move on south to the Ryukyuan royal capital of Shuri, today a district of the city of Naha.

The capital desperately tries to organize a defense, but the kingdom's military capabilities are no match for those of the invaders.

Ryukyu's hereditary aristocratic class, unlike that of the Japanese samurai, is not a warrior class, and in any case the kingdom has faced no threats greater than the occasional pirates in nearly two hundred years.

The invaders enter Shuri Castle on May 6, and loot it, along with a number of nearby temples and noble residences, stealing or destroying Buddhist scriptures and a variety of other objects of religious or historical significance, along with considerable portions of the royal treasure.

Shō Nei surrenders and is taken, along with roughly one hundred of his officials, to ...

...Sunpu to meet with the retired Shogun Tokugawa Ieyasu, ...

...then to Edo for a formal audience with Shogun Tokugawa Hidetada, and ...

...then to Kagoshima, where he is forced to more formally surrender and to declare a number of oaths to the Shimazu clan.

The king and his councilors are made to swear that "the islands of Riu Kiu have from ancient times been a feudal dependency of Satsuma", and that there is a long-standing tradition of sending tribute and congratulatory missions on the succession of the Satsuma lords, though these are all falsehoods.

The oaths also include stipulations that the kingdom admit its wrongdoing in ignoring and rejecting numerous requests for materials and for manpower, that the invasion is justified and deserved, and that the lord of Satsuma is merciful and kind in allowing the king and his officers to return home and to remain in power.

Finally, the councilors are forced to swear their allegiance to the Shimazu over their king.

Tei Dō, a royal councilor and commander of the kingdom's defense against the invasion, refuses to sign the oaths and is beheaded.

The kingdom's royal governmental structures remain intact, along with its royal lineage.

The Ryukyus remain nominally independent, a "foreign country" to the Japanese, and efforts are made to obscure Satsuma's domination of Ryukyu from the Chinese Court, in order to ensure the continuation of trade and diplomacy, since China refuses to conduct formal relations or trade with Japan at this time.

However, though the king retains considerable powers, he is only permitted to operate within a framework of strict guidelines set down by Satsuma, and is required to pay considerable amounts in tribute to Satsuma on a regular basis.

This framework of guidelines is largely set down by a document sometimes called the Fifteen Injunctions, which accompanies the oaths signed in Kagoshima in 1611, and which details political and economic restrictions placed upon the kingdom.

Prohibitions on foreign trade, diplomacy, and travel outside of that officially permitted by Satsuma are among the chief elements of these injunctions.

Ryukyu's extensive trade relations with China, Southeast Asia, and Korea are turned to Satsuma's interests, and various laws are put into place forbidding interactions between Japanese and Ryukyuans, travel between the two island nations.

Likewise, travel abroad from Ryukyu in general, and the reception of ships at Ryukyu's harbors, are heavily restricted with exceptions made only for official trade and diplomatic journeys authorized by Satsuma.

In addition, Amami Ōshima and a number of other northern islands now known as the Satsunan Islands are annexed into Satsuma Domain and removed from the kingdom's territory.

These islands remain today part of Kagoshima Prefecture, not Okinawa Prefecture.