During the planning for President Trump’s latest strike on Iran, Britain refused to allow the United States to launch air attacks from the U.S.-U.K. base at Diego Garcia, an island in the Indian Ocean. Only a few hours’ flying time from the Middle East, Diego Garcia offers airfields long enough for the heaviest bombers and has naval docks large enough for aircraft carriers and nuclear submarines. It is British territory, left over from colonial times, but was jointly developed under a U.S.-U.K. agreement signed in 1966. Britain reversed its veto against U.S. use of British bases yesterday, but only for what Prime Minister Keir Starmer defined as “defensive” strikes. The delay and restrictions have dealt a blow to the U.S.-U.K. alliance. Unfortunately, Starmer’s Labour government seems bent on inflicting even harsher blows very soon.
Britain’s veto seems to have been what prompted Trump’s outburst on Truth Social on February 18, which ended with, “DO NOT GIVE AWAY DIEGO GARCIA!”
With this, Trump plunged into a controversy that has polarized British politics but attracted curiously little attention in the United States: the looming handover of Diego Garcia, the site of America’s most important military base in the Indian Ocean, to Mauritius, an African country that has become economically dependent on China and India. Impelled by postimperial guilt, the United Kingdom has insisted that this deal is an inescapable necessity, given that Mauritius has found support for its claim to Diego Garcia at the International Court of Justice, in The Hague. The treaty is signed but cannot take effect without the backing of the United States, which had at first accepted the British deal as a reasonable solution.
Yet the misgivings are well founded—even if they find an unhelpful voice in Trump’s decision to blast the treaty as an “act of GREAT STUPIDITY.” Escaping the trap that Britain and the U.S. have created for themselves will require far more than rage-posting.
Diego Garcia is the southernmost island in the Chagos Archipelago, which has been ruled by Britain since the early 19th century. The islands are also claimed by Mauritius, some 1,300 miles southwest of Diego Garcia. In May 2025, after decades of dispute and then years of negotiations following the 2019 ICJ ruling, the two sides came to an agreement. Britain would surrender sovereignty over the archipelago to Mauritius. Mauritius would then lease Diego Garcia alone back to Britain for 99 years. Mauritius would gain rights to use the other islands in the Chagos chain, but agreed not to lease any of them to a third nation without British approval.
Proponents say that the treaty protects the base and complies with international law. Opponents counter that Mauritius’s claim to the islands is weak and unenforceable. They worry that the little republic has been granted dangerous rights over U.S. security decisions—and that the country’s strong ties to China and India make it an unreliable security partner for the U.S. and U.K.
Britain has long accepted that the United States must agree to any change to the islands’ legal status. This means that Trump needn’t rant and rave on social media to stop the “give away” of Diego Garcia; he could kill the treaty himself. Yet Trump has not done that. Instead, the Trump State Department has repeatedly endorsed the deal to end British sovereignty over the Chagos Archipelago. Trump himself has praised those negotiations too. Even his February 18 post is phrased as a personal opinion, as if the decision belonged exclusively to Britain. “Prime Minister Starmer should not lose control, for any reason, of Diego Garcia, by entering a tenuous, at best, 100 Year Lease. This land should not be taken away from the U.K. and, if it is allowed to be, it will be a blight on our Great Ally.”
The day of Trump’s online outburst, a reporter asked White House Press Secretary Karoline Leavitt whether the administration now opposed the Chagos treaty it had previously supported. She explained that Trump’s post was the official policy of the U.S. government, “straight from the horse’s mouth.” She did not, however, clarify whether the post amounted to a U.S. veto. In other words, she seemed as baffled as everybody else.
While the world waits to learn whether Trump’s words amount to an actual change of U.S. policy, or are merely a disgruntled man’s opinion, Americans should understand the origins of the Chagos treaty—and its hazards.
Before the arrival of European settlers, both Mauritius and the Chagos islands were uninhabited by humans. Mauritius was named by Dutch explorers for their ruling prince, Maurice; the Chagos were named by Portuguese seafarers, probably for the Portuguese word for Christ’s wounds: chagas.
Mauritius was the home of the famous dodo bird, whose forest habitat would be destroyed by sugar plantations—first under Dutch rule, then French—worked by slaves from Madagascar and mainland Africa. The Chagos were used to farm coconuts, also by slave labor. The British seized both Mauritius and the Chagos islands during the Napoleonic Wars with France, then formalized their sovereignty at the peace conferences that ended those conflicts.
The British Parliament outlawed slave trafficking in 1807, abolished slavery outright in 1833, and then compensated slaveholders. Cash in hand, the sugarcane planters of Mauritius replaced their slaves with contract labor from the Indian subcontinent. As the sugarcane industry expanded, skilled workers and entrepreneurs from India came to manage the needs of the growing colony. When Mauritius became independent in 1968, a large and growing share of its nearly 800,000 residents were of Indian origin.
The atolls and rocks that made up the Chagos Archipelago offered more meager economic possibilities. When slavery ended, the coconut farms paid scant wages to the workers and their children. By the 1960s, fewer than 1,000 people lived in the Chagos Archipelago, almost all of them descendants of enslaved Africans. Whereas Mauritius was four-fifths Hindu or Muslim, the people of the Chagos were almost uniformly Roman Catholic.
For administrative convenience, Britain had ruled the Chagos Archipelago from the Crown colony of Mauritius, as France had done before it. But this presented an awkward problem in the 1950s and ’60s, when the British began decolonizing their African territories. The British had built an airstrip on Diego Garcia during World War II. The Americans now sought to lease and modernize that base. With the advent of long-range bombers, Diego Garcia’s location in the middle of the Indian Ocean was no longer remote, but central. The Americans wanted Britain, not Mauritius, as the landlord for the ambitious air and naval base they had planned. In 1965, the British detached the Chagos islands from Mauritius, then named the archipelago as the British Indian Ocean Territory.
Advocates for Mauritius now complain that this was an unjust act. At the time, however, Mauritius took a more relaxed view. According to an account by the former director of the Seychelles islands’ national archives, the Mauritius colonial government reacted to the British proposition by asking to swap the Chagos Archipelago for ownership of the Seychelles, then another British colony in the Indian Ocean. The British had ruled the Seychelles from Mauritius from 1814 to 1903, then severed it to form a separate colony. (The Seychelles gained independence in the 1970s.) If one severance was legal, why not the other? Upon being told that the return of the Seychelles was impossible, the Mauritius government accepted 3 million pounds in compensation for the Chagos chain, about $100 million today.
The Americans, worried about a future independence movement on the Chagos islands, insisted that the new British Indian Ocean Territory be emptied of its residents. The British duly closed the last of the coconut farms and, from 1967 to 1973, removed the Chagossians to Mauritius and the Seychelles, where many suffered extreme poverty. The constitution of the British Indian Ocean Territory specifies that no one has a right of abode on the islands. My Atlantic colleague Cullen Murphy has written movingly about the sense of displacement felt by the Chagossians and their descendants to this day.
In 1972 and 1982, the British government put millions more into a trust fund for the hundreds of Chagossians removed to Mauritius. (The Chagossians in the Seychelles got nothing.) The 1982 payment was presented by Britain as a “final settlement.” Mauritius at first took the view that the funds were meant to offset the government’s costs of absorbing the Chagossians. When payments did at last flow to Chagossian families, their value was much corroded by the inflation of the Mauritian rupee.
In time, Chagossians found ways to immigrate to Britain. They built a community in West Sussex, near Gatwick airport, where many found work. Because British Chagossians were largely concentrated in one parliamentary constituency, their plight became a political matter. In 2002, an act of Parliament granted British citizenship to Chagossians and their children in Britain, amounting to a few thousand people. Groups of British Chagossians have lately engaged in acts of civil disobedience to reassert a right to return to the outer Chagos islands, but as British citizens living under British law on British soil.
Mauritius is one of the most successful countries in the 55-member African Union. Its GDP per capita is second only to that of the Seychelles. Elections occur regularly, most recently in November 2024, and human rights are generally well respected. Yet Mauritius faces many of the familiar problems of a postcolonial society. For more than half of its independent existence, it has been ruled by two generations of a single family named Ramgoolam. Corruption is a serious concern: A former prime minister and a former chief of the central bank were arrested in 2025 on money-laundering charges.
Still, Mauritius’s domestic policies are more in line with American values than those of say, Qatar, which hosts large U.S. installations. Mauritius’s foreign policy is what makes the country an uncomfortable landlord for a major American military base. Mauritius signed a free-trade agreement with China in 2019, China’s first with any African nation. The Chinese communications company Huawei chose Mauritius as its African regional hub. China financed the modernization of Mauritius’s airport, financed and built the country’s most advanced dam, and covered much of the cost of Mauritius’s largest stadium and sports center in 2018. Tiny Mauritius is now one of the top five African destinations for Chinese investment, which is especially impressive given that it is the only one of the five with no mineral resources to develop. Mauritius has received two visits by Chinese presidents: Hu Jintao, in 2009, and Xi Jinping, in 2018. In February, The Telegraph reported that more than 6,000 Mauritian officials had received various forms of training from China.
India, too, has financed important infrastructure projects in Mauritius. Mauritius’s national security adviser and the head of its naval force are both Indian military officers. In 2015, Mauritius leased the island of Agalega—870 miles west of Diego Garcia—to India for development as an air and naval base. Although India is more or less a security partner of the United States and Britain today, that alliance may not always hold.
Mauritius’s deals with China and India may well make sense for a small country trying to succeed in a region where the two emerging powers loom large. But how much sway do Americans want to grant an island nation that is attempting to appease China and India over a territory that hosts the U.S. Navy and Air Force?
Although the agreement that Britain negotiated forbids Mauritius from leasing other Chagos islands to anyone else, nothing is stopping the country from building its own eavesdropping stations and selling the information to buyers in Beijing or New Delhi—among many other concerns raised by China- and India-watchers.
For a long time, Mauritius’s claims on the Chagos islands made only slow diplomatic progress. But in 2017, Mauritius was able to elevate a resolution about the matter to the United Nations’ General Assembly agenda, urging that the conflict over these islands be referred to the ICJ. The motion was well timed. Britain had voted the year before to leave the European Union—burning goodwill with many former partners. And Trump, America’s new president, had just scolded U.S. allies at his first NATO summit in Brussels. So when Mauritius made mischief, America and Britain discovered themselves short of friends. The UN resolution was adopted by a vote of 94 yeses, 16 no’s, and 65 abstentions. Among those abstaining: nearly every EU member state, plus non-EU NATO partners including Canada, Iceland, and Norway.
The matter duly went to the ICJ, which ruled in Mauritius’s favor in February 2019. The ruling was strictly an advisory one. But through a series of deft legal maneuvers—joined to the ever more ambitious self-concepts of some international legal tribunals—Mauritius was able to win a second legal victory at another international tribunal, for the law of the sea. The British government interpreted these trends as deeply ominous for its hold on the Chagos Archipelago.
In 2022, Britain announced that it would enter negotiations with Mauritius. The election of a Labour government in 2024 accelerated these negotiations. It probably did not hurt that the lead lawyer for Mauritius at the time, Philippe Sands, is a close friend of Prime Minister Starmer’s and a former law partner of Britain’s attorney general, Richard Hermer.
The ICJ advisory ruling condemned Britain’s severance of the Chagos islands as a “failure” of decolonization. Yet Mauritius’s ambitions are no less colonial. Heedless of the wishes of the Chagossian diaspora, Mauritius wants to reach across a thousand miles of ocean to claim territory to which it has few ties other than the clerical imperatives of a bygone imperial administration. Mauritius’s motive is not about peoplehood but about power: A Mauritian sovereignty over the Chagos will yield more income and influence than Mauritius would on its own.
In the past, the reach of international public law was limited by the ancient rule that no government can be bound by an international tribunal without that government’s consent. But some international jurists imagine international public law as a force that can and should evolve, apart from and even independent of governments. They imagine this evolution as a force that can replace grim power politics with ideals of justice, that can restrain the strong and empower the weak. For them, Mauritius’s maneuvers to adjudicate the status of the Chagos islands despite British objections offer a thrilling glimpse of a better future.
The Chagos Archipelago case also exposes the core weakness of the new approach to international public law. The methods used here would obviously be futile against China. China occupies islands across the South China Sea without even a figment of legal right. No court decision will pry loose any of those holdings. China holds Tibet without noticeable bother, commits crimes against its Uyghur Muslim minority with impunity, launches acts of aggression against its neighbors in the South China Sea, and growls off any court or tribunal that looks askance—which few do. As China gets stronger, illusions about what international public law can do become both more dangerous and more absurd.
The Chagos treaty demands considerable payments from Britain to Mauritius: 101 million pounds a year, on average, for 99 years, much more in the early years of the agreement, with complex adjustments for inflation along the way. The British government estimates the net present value of the payment stream at 3.4 billion pounds, but critics counter that the true cost will be much higher. Regardless, Mauritius has collected payments from Britain before, in 1965, 1972, and 1982, without feeling bound to stop asking for more.
The text of the agreement, which calls on each party “to ensure that in the implementation and application of this Agreement, including activities in relation to the Base, there shall be compliance with international law,” makes it easy for Mauritius to tangle the U.S. and the U.K. in litigation anytime Mauritius (or any future ally or patron of Mauritius) wishes to thwart U.S. military action from Diego Garcia.
Some may say that the U.S. has more than enough military and economic clout to enforce its rights against a tiny country like Mauritius. But 20 years from now, if and when China and India have grown only more powerful, the U.S. may find its clout diminished. The treaty essentially signs up the U.S. and U.K. for shakedowns forever. The British government is currently too naive to imagine Mauritius abusing the treaty this way. Trump, however, is cynical enough to foresee these future threats to the Anglo-American advantage of the status quo.
Which brings us back to Trump’s rage-posting. What does it accomplish? It does not veto the treaty. But Trump’s social-media opposition does create a domestic political problem for Starmer. The British prime minister’s net approval ratings have plunged in recent months to the lowest levels ever tracked by British polling. The beneficiary of this plummet is Britain’s right-wing Reform Party, a kind of MAGA proxy, led by Trump’s longtime ally Nigel Farage. Reform cites the Chagos treaty as proof of the fecklessness and weakness of not only the Labour Party but also the Conservatives, who began negotiations with Mauritius. In short, Trump’s outbursts are doing much more to boost the U.K.’s MAGA franchise than defend America’s strategic position in the Indian Ocean.
Yet Chagos still amounts to one of those rare cases where Trump may break something that actually deserves to be broken.
The goal of U.S. and U.K. diplomacy over Diego Garcia should be to end Mauritius’s pretensions over the Chagos islands, not legitimize them. The genuine wrongs to the exiled Chagossians should be righted, but not by accepting a territorial wish list to supposedly benefit people who never wanted to be governed by Mauritius in the first place. Guilt for European imperialism in the 19th and 20th centuries should not become the permission structure for new forms of imperialism.
Most Chagossians say in polls that they want to be British. Some may wish to become Americans. Any money to be paid for the benefit of Chagossians should be paid to Chagossians directly. Any money for Mauritius should be paid to extinguish Mauritius’s claims—to make truly final the settlements reached in 1965, 1972, and 1982—while leaving the Chagos Archipelago securely and exclusively in British hands.
Under the American and British flags, Diego Garcia defends the Indo-Pacific region against aggressors who do not trouble their consciences about laws, pacts, or the rights of weaker nations. That’s more than enough moral justification to keep the old flags flying.