Okinawa Prefecture (Japanese: 沖縄県, Hepburn: Okinawa-ken, Okinawan: ウチナーチン Uchinaa-chin) is the southernmost prefecture of Japan. It comprises hundreds of the Ryukyu Islands in a chain over 1,000 kilometres (620 mi) long. The Ryukyus extend southwest from Kyushu (the southwesternmost of Japan's four main islands) to Taiwan. The Okinawa Prefecture encompasses the southern two thirds of that chain. Naha, Okinawa's capital, is located in the southern part of Okinawa Island. Currently about half of the 53,000 U.S. troops deployed in Japan as part of the post-WWII security arrangement are based in Okinawa.