The first island chain refers to the first chain of major Pacific archipelagos out from the East Asian continental mainland coast. It is principally composed of the Kuril Islands, the Japanese archipelago, the Ryukyu Islands, Taiwan (Formosa), the northern Philippines, and Borneo, hence extending all the way from the Kamchatka Peninsula in the northeast to the Malay Peninsula in the southwest. The first island chain forms one of three island chain doctrines within the island chain strategy in the U.S. foreign policy.[1][2]
Much of the first island chain is roughly situated in waters claimed by China.[3] These include the South China Sea, within the nine-dash line, as well as the East China Sea west of the Okinawa Trough.