The Okinawa Noodle Manufacturing Co-op negotiated with the Fair Trade Commission and as a result it was accepted as one of several exceptions under the name of "Okinawa soba". Some attempt to trace the origin of Okinawa soba to the Ryūkyū Kingdom period. Chinese delegates possibly brought wheat noodles to the royal court, though no link has been established to the modern Okinawan cuisine. The first known documented reference to Okinawa soba was in 1902 during the late Meiji period when it was known as "Shina soba" (Chinese "soba") as in mainland Japan. Several soba restaurants are known to have operated in Naha during the Taishō period and to have close links with the red-light district. Soba restaurants were destroyed by U.S. attacks during the Battle of Okinawa. Its revival began in U.S. internment camps, where wheat rations were supplied. In the 1960s, soba was popularized with the introduction of noodle making machines. The popularization was accompanied by the transformation from a restaurant meal to home cooking. The mainland Japanese custom of eating soba on New Year's Eve was introduced to Okinawa in 1968, but buckwheat noodles were replaced by wheat noodles. Today, Okinawa soba is considered as a vital part of traditional Okinawan culture, although folklorist Nishimura Hidemi argued that it was an invented tradition. The soba has been adopted as a local tradition in Campo Grande in the state of Mato Grosso do Sul, Brazil, due to the large Okinawan-descended population in the city of 850,000. It's usual to find specialized restaurants along the city serving a local adaptation of the dish due to the difficulty of finding seafish in that region of Brazil.