Has Okinawa been a part of Japan from ancient times?

Okinawa was not a part of Japanese territory at the time of the Meiji Restoration(1868), the dawn of the modernization of Japan.
Okinawa' s former name, Ryukyu, was given by the Chinese.
The Ryukyu Kingdom existed from the beginning of the 15th century, but since it was a weak country, it sought support from both the Ching Dynasty of China and the Satsuma Clan of Japan.
In 1872, the Japanese government tried to incorporate Ryukyu into Japan and in 1879 they changed its name to Okinawa Prefecture without any protest from the Ching government.

Visitors may get the impression that Okinawa is both physically and spiritually a mixture of Japan, China and Southeast Asia.
The language, however, called the Ryukyu dialect, is considered to be similar to Japanese, although it sounds different from the other Japanese dialects.