Han Xingfang, former deputy director of Lushun Museum and a longtime researcher on the subject, wrote in an article that the phrase "suffered harassment from a neighboring state" in the edict refers to the 1612 incident, in which Japan sent 3,000 troops to invade Ryukyu and captured King Shang Ning.

This dark episode in Ryukyu's past is also recorded in the chronicle The History of the Ming Dynasty, the accounts of which say that the Ryukyu king was later released and the kingdom resumed its tribute missions.

According to Han, the Ming Dynasty conducted a total of 15 investiture missions to Ryukyu, with the one issued during Emperor Chongzhen's reign being the last.

Ryukyu's tributary relationship with China continued during the Qing Dynasty (1644-1911).

In the 11th year of Emperor Shunzhi's reign (1644-1661), King Shang Zhi of Ryukyu sent envoys to Beijing to return "two old imperial edicts, one imperial decree and a gilded silver seal", and to request new investiture documents and seals.

Through this envoy mission, the edict made during Emperor Chongzhen's reign eventually made its way back to China.

Xinhua contributed to this story.

Contact the writers at zhangyunbi@chinadaily.com.cn