Okinawa Prefecture is the southernmost prefecture of Japan. It comprises hundreds of the Ryukyu Islands in a chain over 1,000 kilometres long. The Ryukyus extend southwest from Kyushu 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.