Whether Ramadan was ethnically Korean is unknown. After the Mongol conquest of Korea in the thirteenth century, many Central Asian Muslims (called "semu") entered the country—then ruled by the Goryeo dynasty as Mongol vassals—to serve in the Mongol and Korean administrations or to engage in commerce. These Muslims established a local community in the Korean capital of Kaegyong, where they constructed a mosque and enjoyed significant cultural and religious autonomy until a royal decree ordering forcible assimilation was passed in 1427. As the Mongols frequently appointed "semu" but rarely ethnic Koreans as local governors, Ramadan may have been a Muslim of Central Asian (perhaps Uyghur) ethnicity who was simply born or had settled in Korea. As Rongzhou was a center of trade with Trần Vietnam, historian Lee Hee-soo speculates that Ramadan may have been an international "semu" merchant based in Korea who was hired by the Yuan.