Indian Ocean Bases

What it is

The Indian Ocean carries roughly half the world's seaborne trade, connects Persian Gulf oil exporters to East Asian factories, and sits between three nuclear powers: India, Pakistan, and China. A fourth, the United States, projects force across the ocean from the far Pacific. Military bases around its rim and on its islands determine who can strike, supply, and surveil which targets. Five countries hold active basing positions as of mid-2026: the United States at Naval Support Facility Diego Garcia in the British Indian Ocean Territory and at Camp Lemonnier in Djibouti; China at Doraleh in Djibouti and Ream in Cambodia; France at La Réunion and Djibouti; India at its Andaman and Nicobar Islands Command; and Australia at HMAS Stirling in Western Australia under the AUKUS arrangement.

History

The United States and the United Kingdom created the British Indian Ocean Territory (BIOT) in 1966 by excising the Chagos Archipelago from Mauritius before granting that country independence, and forcibly relocating roughly 1,500 Chagossian residents. Naval Support Facility Diego Garcia opened in 1971 and supported US B-52 strikes in the 1991 Gulf War, the 2001 Afghanistan campaign, and the 2003 Iraq invasion. The 1971 UN General Assembly resolution declaring the Indian Ocean a Zone of Peace was never given practical effect.

China entered the region in 2008 under the cover of Gulf of Aden anti-piracy operations, dispatching naval task forces at roughly three rotations per year. In 2017, Beijing opened a formal military facility at Doraleh, Djibouti, 13 km from US Camp Lemonnier. The same year, China Merchants Port Holdings secured a 99-year lease on Sri Lanka's Hambantota port for approximately US$1.1 billion, positioning it (81°E) to flank Diego Garcia (72°E) to the east, as Gwadar, Pakistan (62°E) flanks it to the west.

Current state

Diego Garcia hosts approximately 2,500 US personnel, B-2 and B-52 bombers, satellite ground stations, and pre-positioned munitions. On 20 March 2026, Iran launched two intermediate-range ballistic missiles at the atoll from over 2,300 miles away, the first confirmed strike on the base; both were intercepted. The attack demonstrated Iran had surpassed its previously self-imposed 1,250-mile strike range limit. In May 2025, the UK and Mauritius signed an agreement granting Mauritius sovereignty over the Chagos Archipelago while preserving a 99-year UK lease over Diego Garcia, backed by approximately US$4.5 billion in payments. The deal had not entered into force as of mid-2026; the US Trump administration has objected on national security grounds.

China's second overseas installation, at Cambodia's Ream naval base, became operational in April 2025, extending People's Liberation Army Navy reach toward the Strait of Malacca.

India has accelerated Andaman and Nicobar Islands Command infrastructure under its Indian National Maritime Security Strategy (INMSS-2026), committing Rs 150 billion to forward landing grounds and radar networks, as documented in the India IOR grey-zone build-up. The Quad's Indo-Pacific Maritime Surveillance Capability, launched in May 2026, adds a shared vessel-tracking layer above the physical posture, per the Quad IPMSC announcement. Under AUKUS, US and UK nuclear-powered submarines are due to begin rotational deployments to HMAS Stirling from 2027, per the May 2026 AUKUS ministers' settlement.

Relationships

Diego Garcia anchors US power projection into three operational theatres: the Middle East, East Africa, and the western Indian Ocean approach routes. China's dual-use port arc from Gwadar through Hambantota to Ream constitutes what strategists call a "string of pearls," with Djibouti the sole confirmed military node so far. India's Andaman and Nicobar Command sits at the Bay of Bengal's mouth, positioned to monitor and constrain PLAN transit through the Malacca Strait. HMAS Stirling locks Australia into the network as the southern anchor.

What to watch

• Whether the UK-Mauritius Chagos deal enters into force; Trump administration opposition has created legal ambiguity about Diego Garcia's long-term authority structure.
• China's third overseas base: East Africa and the Arabian Sea remain the most frequently cited candidate regions, with US officials tracking roughly 18 countries.
• India's Andaman forward landing ground buildout timelines, set against a Chinese survey-vessel pressure campaign documented in the grey-zone escalation reporting.
• AUKUS nuclear-submarine rotations at HMAS Stirling from 2027, which would mark the first persistent allied nuclear submarine presence in the Indian Ocean south of the equator.