If Britain wants to remain a reliable partner in our security alliance, it must be willing to defend its sovereignty.

    As much as President Trump uses unpredictability as a diplomatic tool, I can predict one thing for sure: there is no way he will allow Britain to give up its sovereignty over the Chagos Islands. The real question is why Britain would cede such sovereignty in the first place.

    Claiming that international law and Britain’s reputation demanded it, the United Kingdom announced a deal in October that would give the Republic of Mauritius sovereignty over the Chagos Islands, a British Overseas Territory. Since the 1970s, the UK and the United States have jointly operated the Diego Garcia military base on the largest island in the Chagos Archipelago, making the possibility of Mauritian sovereignty a national security concern for America.

    By January, negotiators reached a framework in which the UK would transfer sovereignty to Mauritius while leasing the Diego Garcia base for ninety-nine years with an annual payment of £90 million. After discussions stalled during the American presidential transition, both sides recently announced renegotiated terms: Britain will front-load its payments and adjust them for inflation, effectively doubling the price tag. Furthermore, negotiators removed a clause that would allow the UK to unilaterally extend the lease by forty years, giving Mauritius the opportunity not to renew the lease.

    The current framework requires a final review by the United States. While the Biden administration previously signaled approval of the agreement, the Trump administration is almost certain to block it. Secretary of State Marco Rubio described the treaty as a “serious threat,” and Robert Wilkie, head of Trump’s Pentagon transition team, said “it was a calamitous decision.”

    America will step in to prevent the UK from casting aside its territory and threatening the national security of both countries, but we shouldn’t have to. Britain is one of our closest allies and a permanent member of the UN Security Council—they should act like it. Amid fighting in Ukraine and rising tensions in the Indo-Pacific, it’s time for the UK to get serious about its defense. If Britain wants to remain a reliable partner in our security alliance, it must be willing to defend its sovereignty.

    Beyond the issue of leasing its own territory, Britain’s Chagos deal would open the islands to Chinese influence. Mauritius and the People’s Republic of China have particularly close ties. In 2019, it became the first African country to sign a free trade agreement with China, and Huawei has built a substantial presence on the island. While it is not a part of the Belt and Road Initiative, it doesn’t need to be in order to threaten the Diego Garcia base. Britain has historically been able to keep away commercial vessels from the 250,000 square mile Chagos Marine Protected Area. Even with a British lease on the Diego Garcia installation, Mauritius could open the surrounding waters to Chinese fishing and grey zone disturbance tactics.

    Britain took over the governance of both the Chagos Islands and Mauritius from France in 1814. As it unwound its colonial governance in the region, the Chagos Islands became the British Indian Ocean Territory in 1965, while Mauritius became independent three years later. In the following years, the British developed Diego Garcia into a military site and forcibly relocated many Chagossians. Mauritius has long claimed sovereignty over Chagos, but for decades, the UK has denied their claims. It’s not as if Chagos and Mauritius are even geographically close—Mauritius and the Chagos Archipelago are more than 1,300 miles apart. The only reason that the two were ever under the same governance was due to the British strategy of governing its Indian Ocean island holdings collectively.

    The UK and Mauritius entered negotiations over Chagos in 2019 after the International Court of Justice issued an advisory opinion that stated the UK “has an obligation to bring to an end its administration [of the Chagos Islands] as rapidly as possible.” To be clear, an advisory opinion from the ICJ is not binding—there would be no consequences if the UK were to ignore it. Negotiations stretched for years until, under the leadership of Prime Minister Keir Starmer and Foreign Secretary David Lammy, a deal was reached.

    Lammy emerged as a particularly strident proponent of the deal, emphasizing two arguments in its defense. First, he claimed that the future of the Diego Garcia military was in jeopardy after the 2019 ICJ ruling. Second, he argued that continued control of the Chagos Islands would violate international law at the cost of Britain’s reputation around the world. Both arguments display a detachment from reality.

    Britain’s control of the Chagos Islands is neither threatened by Mauritius nor the ICJ. The British government can choose to act in service of its national interest—one might even argue that they have an obligation to do so. Lammy would surely argue that the Chagos deal is in the national interest. Without an agreement, the theory goes, Britain’s good standing in the eyes of the world would be diminished. He stated as much in an October statement: “We are showing that what we mean is what we say on international law and desire for partnerships with the Global South.”

    This obsession with reputation is directly tied to Britain’s misguided focus on soft power in place of force projection. In January, Lammy launched the UK Soft Power Council, an advisory board to provide “advice on the development of a forward plan for government campaigns that promote the UK image and offer to the world, drawing on the breadth of UK strengths, including diversity.” But soft power is just that: soft. The truth is that goodwill, which can supplement power, is not a replacement for raw capacity to act. With a new administration in Washington that is already skeptical that our European allies take their defense seriously, Britain’s leadership exhibits a misalignment of priorities.

    As an American studying in the UK, I was confused to read about the deal’s details, which emerged during the back-and-forth negotiations between October and January. Surprisingly, the British students with whom I discussed the agreement were equally puzzled. Why would Britain give Chagos to Mauritius—and pay £90 million every year for the privilege of doing so? Amid dismal growth and a possible £30 billion budget gap, Britain can hardly afford to spend billions to buy the favor of the Mauritians. And at this time of heightened geopolitical tensions, they can hardly afford to treat their security with anything other than the utmost seriousness.

    America will step in to put an end to this disastrous deal, but this will not address Britain’s apparent disregard for its own sovereignty. The Anglo-American military presence in the Indian Ocean can withstand complaints from Mauritius and Chinese maneuvering. In simple terms, the only threat to the future of the Diego Garcia base is Britain. A consensus is forming in Washington that European allies should do more to ensure their defense—especially the UK. The next four years will be pivotal for determining Britain’s role in the twenty-first century. They should choose to be a serious, reliable ally, and they should be willing to do so on their own terms.

    Farrell Gregory is the chief editor of the Oxford Emerging Threats Journal and a research assistant at the Yorktown Institute. He is currently a visiting student at Mansfield College, Oxford, studying politics, philosophy, and economics.