Responsible Statecraft has reported:

Diego Garcia remains central to the United States’ military position in the Indian Ocean, a role underscored in March when Iran fired two missiles at the island during the ongoing war. Both missiles missed, but the attack provided the first operational demonstration of Iran’s intermediate-range ballistic missile capability. The island hosts a joint British-American base about 2,500 miles from Iran, and its strategic importance is the focus of a new history by Samuel Bashfield.

Bashfield’s book, titled “The British Indian Ocean Territory,” examines the United States’ and United Kingdom’s Cold War activity in the region. The attack also recalled how security in the Indian Ocean is tied to the wider Middle East. Decades earlier, a senior American naval official described the ocean as the Middle East’s “backdoor” and the “soft underbelly” of Russia and China.

Diego Garcia supports naval logistics, air power, prepositioned military supplies and intelligence gathering. It serves as a hub for operations across the Indian Ocean, the Middle East, South Asia and Africa. Bashfield calls it “a coveted lily pad,” while the book’s reviewer compares its place in American strategy to Guam’s role in the Pacific.

Bashfield drew on archives in the United States, Britain and Australia. Some records remain confidential under government rules, but the documents he consulted trace the island’s strategic importance from the Second World War onward. Bashfield holds a doctorate in maritime history and national security policy.

The book begins with Diego Garcia’s contribution to the Allied war effort. Japan’s rapid advances in Southeast Asia threatened British Singapore, and in 1941 Britain decided to use Diego Garcia as a naval logistics base covering the Indian Ocean.

Military planners in Britain and the United States more fully grasped the value of Diego Garcia and the wider Chagos Archipelago during the early Cold War, as countries in Asia and Africa moved toward independence. The Indian Ocean Task Force of 1959, America’s Strategic Island Concept of 1960 and Britain’s Island Strategy of 1963 set out the thinking behind the islands’ strategic importance.

Bashfield recounts British-American negotiations over the Chagos Islands and Diego Garcia, including their detachment from colonial Mauritius and Seychelles. In the late 1960s, London and Washington sought to secure each other’s position in the Indian Ocean. The book also examines Aldabra, a lesser-known island that British planners considered as a possible military facility.

Over time, the two countries made three quid pro quo agreements linking expanded American access to Diego Garcia with support for Britain’s nuclear deterrent. In return for a larger American presence on the island, Britain received US assistance with three successive submarine-launched ballistic missile programmes: Polaris, Super Antelope and Trident.

Those weapons helped Britain remain a nuclear power, maintain a second-strike capability and strengthen its undersea deterrent. The history therefore also explores Britain’s nuclear policy. Then-prime minister Margaret Thatcher said her decisions on nuclear technology carried “the greatest long-term consequences for Britain.”

In the book’s later chapters, Bashfield describes Diego Garcia’s “coming of age” as American military infrastructure expanded over decades. He argues that the British Indian Ocean Territory has become a “de facto American territory,” although officials in London have at times expressed concern about sovereignty.

The base became a key logistics hub and airbase during Operations Desert Shield and Desert Storm, following Saddam Hussein’s unprovoked invasion of Kuwait in 1990. Its use in those operations added to its established role supporting missions across several regions.

The reviewer says the book could have offered more on the international setting around the British-American negotiations, particularly the perspectives of other major actors. Bashfield discusses the roles of the Soviet Union, India and some other littoral states, but those accounts are not fully developed.

Britain is now working to dissolve the British Indian Ocean Territory and facilitate Mauritian sovereignty over the Chagos Archipelago. US President Donald Trump has added uncertainty by criticizing British officials for signing what he called a “stupid” deal to return the island chain to Mauritius. Secretary of State Marco Rubio has described the agreement as “historic” and supported Britain and Mauritius in their negotiations.

Under the agreement, Mauritius would gain sovereignty over the entire archipelago, while the United Kingdom could operate the Diego Garcia base through the United States for an initial 99 years, with a possible 40-year extension. London would pay Port Louis £3.4 billion, or US$4.5 billion, over the next few years.

The negotiations also sit alongside the history of the Chagossians, the archipelago’s native people. Starting in the late 1960s, they were forcibly displaced to clear military sites in the British Indian Ocean Territory. Legal battles that began in the early 1970s remain ongoing in British courts.

For British and American military establishments, Diego Garcia remains essential amid naval rivalry in the Indian Ocean and China’s expanding presence in those waters. Losing access could have long-term consequences for their regional position. At the same time, Mauritian sovereignty and territorial integrity, along with the claims of exiled Chagossians, remain pressing issues. Bashfield suggests those aims need not conflict, though the dispute continues to shape the future of the island at the centre of the Indian Ocean.