 Why the US is overhauling its marines on Japan's Okinawa? Tokyo, the United States plans to shake up its marine force on Japan's Okinawa Islands as Tokyo undertakes its biggest military build-up since World War II. That will double defense spending over five years, to deter China from attacking Taiwan or nearby Japanese islands. Japan and the United States want to reinforce the islands separating the East China Sea from the Western Pacific. Because they are close to Taiwan and form part of what military planners refer to as the first island chain extending down to Indonesia, that hams in China's forces. There are approximately 18,000 marines in Japan. The US military presence in Okinawa includes most of the marines stationed in Japan. American bases cover around 8% of the main Okinawa island. The marine core bases in Japan include Camp Kortney, Camp Foster, Camp Fuji, Camp Gonsolves, Camp Hanson. The headquarters for MCI PAC, which consists of two air stations and 10 camp-slash housing areas throughout Okinawa, and mainland Japan, resides aboard Camp Foster in Okinawa. In January, American and Japanese diplomats decided that the US military needed to boost its presence in Japan. This includes placing more forces there with the ability to conduct intelligence, surveillance, and reconnaissance.