Island-Chain Bases

What it is

The island chains are three arcs of Pacific islands that define US strategic geography in the Indo-Pacific. The first runs roughly 5,000 kilometres from Japan's Ryukyu Islands (including Okinawa) through Taiwan and the Philippines to Indonesia, forming a natural barrier along China's eastern coastline. The second extends further east: the Bonin and Volcano Islands, the Mariana Islands (including the US territory of Guam), Palau, and western Papua New Guinea. A notional third anchors at Hawaii. Together these arcs determine how the United States projects power toward East Asia, and how China's navy must break through to reach the open Pacific.

As of mid-2026, US Indo-Pacific Command (INDOPACOM) operates approximately 40 bases west of the international date line, spanning Japan, South Korea, Guam, and the Philippines, with coalition arrangements extending the posture into Australia and Pacific island states.

History

US Secretary of State John Foster Dulles first articulated the containment concept in 1951, framing Pacific island arcs as platforms from which to box in the Soviet Union and China using naval and air power. The idea shaped the post-war basing network in Japan, where roughly 55,000 US military personnel and civilians are stationed today, the largest concentration on Okinawa, where Kadena Air Base hosts the largest US Air Force wing in the Pacific.

The closure of Subic Bay Naval Station and Clark Air Base in the Philippines in 1991, after the Philippine Senate voted against renewing the bases treaty, left a gap the United States spent three decades refilling. The 2014 Enhanced Defense Cooperation Agreement (EDCA) restored access to Philippine installations; the Marcos Jr. government expanded it to nine agreed locations in 2023, including Cagayan province in northern Luzon, the site nearest to Taiwan. Guam grew as the second-chain anchor. A 2023 Pentagon five-year, US$7.3 billion military construction plan covers Andersen Air Force Base, Naval Base Guam, and Marine Corps Base Camp Blaz, the first new Marine base built since 1952. The US Department of Defense controls roughly 25 percent of Guam's land area, and defence spending equals approximately 41 percent of the territory's GDP.

Current state

The US military is actively redistributing forces within the chains to complicate Chinese targeting. Marines began relocating from Okinawa to Guam in December 2024. Japan committed to doubling its defence budget to 2 percent of GDP by 2027 and is reorganising its Self-Defense Forces into a new joint operations command whose responsibilities align directly with US basing on Okinawa and the southern Ryukyus. The US is constructing facilities at EDCA sites in Cagayan and Palawan, the northern Luzon locations specifically oriented toward Taiwan contingency operations.

Australia has joined the basing architecture through AUKUS. The Submarine Rotational Force-West, scheduled for establishment at HMAS Stirling in Western Australia in 2027, extends the effective network south of the second chain. Exercises such as RIMPAC knit allied navies into the island-chain posture.

Relationships

The Nakamal Agreement, signed on 29 June 2026, illustrates the contest for island-chain access: Australia committed AU$500 million over a decade to Vanuatu in exchange for a ban on foreign military infrastructure, blocking China from securing a South Pacific foothold. The May 2026 AUKUS ministerial in Singapore confirmed three Virginia-class submarines for Australia, reinforcing the network's southern anchor.

China's anti-access/area denial posture, built around ballistic and cruise missiles and expanding People's Liberation Army Navy surface and submarine forces, aims to deter or defeat US power projection into the first chain, particularly around the Taiwan Strait. The US Department of Defense's 2025 annual report to Congress assessed China's ability to operate beyond the first island chain as modest but growing.

What to watch

• Whether the nine Philippines EDCA sites become permanent fixtures or remain dependent on Manila's domestic politics and its bilateral relationship with Beijing.
• SRF-West establishment at HMAS Stirling in 2027 and whether Australian public support holds as AUKUS lifecycle costs become visible in successive budgets.
• Japan's joint operations command reform and its translation into real INDOPACOM interoperability in a Taiwan contingency.
• PLA exercises in the Philippine Sea probing second-chain defences, and the pace at which China extends anti-access reach east of Guam.