Last month, the United States deployed two B-52 bombers to the Indian Ocean as part of its Pacific Air Forces’ training program. According to the U.S. Air Force, the engagement was part of a mission to strengthen readiness and deterrence in a region that has become an increasingly contested part of the world, whether it’s the Houthi attacks on vessels sailing through the Bab el-Mandeb Strait or the Association of Southeast Asian Nations’ military drills in the Strait of Malacca.
The Indian Ocean is a critical theater for global trade and geopolitical competition. It is home to 33 nations, accounting for 2.9 billion people, more than one-third of the world’s bulk cargo traffic, and two-thirds of the world’s oil shipments. Unsurprisingly, it has become a growing focus of Washington’s Indian Ocean strategy, at the core of which lies the disputed island of Diego Garcia.
Why is Diego Garcia important?
Situated along major international trade routes between Asia and Africa, Diego Garcia is the largest and southernmost of around 60 islands in the Chagos Archipelago, about 300 miles south of the Maldives.
Thanks to its vital location, the island houses a military base that served as a critical node for American air operations during the Gulf War and the wars in Iraq and Afghanistan. Post-9/11, it has also been allegedly used as a detention center by the CIA.
Today, the island is controversial for another reason: It is part of an ongoing sovereignty dispute between the United Kingdom and Mauritius. The tussle presents a dilemma for Washington, which is torn between its military ambitions and its commitment to a rules-based international order.
A successful resolution to the Diego Garcia spat would affirm Western commitment to a free and open Indo-Pacific. If left unresolved, however, the issue could drive countries such as Mauritius to seek redress with alternative partners like China. In 2019, China signed a free trade agreement with Mauritius—its first free trade agreement in Africa. Since then, Chinese real estate and smart-city investments in the country have risen to about $2 billion.
Why is Diego Garcia contested?
For centuries, the Chagos Archipelago was subject to the whims of colonial tussles, thanks to its advantageous location and trade links. In an effort led by the U.S., in 1964, anticipating that Mauritius, then a British colony, would seek independence, the United Kingdom formulated plans to detach and retain the Chagos Archipelago as the British Indian Ocean Territory.
The United Kingdom and pre-independence Mauritius agreed to the conditional sale of Chagos, and, in exchange, Mauritius was promised continued fishing rights and access to the archipelago, which its residents depended on for their livelihoods.
The detachment was motivated by a joint effort from the United States and United Kingdom to establish a military base in Diego Garcia. More specifically, the U.S. sought a base in the Indian Ocean to contain the Soviet threat during the Cold War. In return for the leasing agreement, London received a $14 million discount on U.S.-made nuclear weapons.
Upon the declaration of Mauritian independence in 1968, the Chagos Archipelago and its residents remained a part of the United Kingdom. However, the detachment of Chagos violated multiple U.N. resolutions on decolonization, including one that banned the breakup of colonies before their independence. As leading proponents of the United Nations, continued American and British indifference toward such widely supported resolutions raised questions about whether the international order could protect the interests of other nations.
The dispute expanded in the early 1970s, when the United States and United Kingdom forcibly removed all the remaining inhabitants across the archipelago and began construction of the military facility. Chagossians were sent to the Seychelles and Mauritius, where many faced extreme poverty and discrimination.
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In 2000, the British High Court found that the forceful eviction of the Chagossians had been illegal and granted them immediate right of return to any islands except Diego Garcia. At the time of the ruling, British and U.S. officials opposed the plan for resettlement and, in 2008, the House of Lords overturned the court ruling in favor of the British government.
In addition to the unlawful eviction of the islanders, the British government established a marine protected area around the archipelago in 2010 that banned all fishing in the waters surrounding Chagos—reversing the United Kingdom’s commitments to Mauritian fishing rights. Notably, the government made an exception for the island of Diego Garcia and its territorial waters—allowing those living on the military base to engage in recreational fishing, which contributed to increased illegal fishing and pollution.
Over time, this dispute has also become entrenched in regional debates over nuclear proliferation. In 1996, Africa established a nuclear weapons-free zone under the Treaty of Pelindaba, which includes three supplementary protocols for non-African nuclear powers to commit to the treaty. In April 1996, Mauritius became a party to this agreement, and as nuclear weapons states, this meant that the United Kingdom and United States also needed to adhere to the treaty.
According to a map appended to the treaty, the nuclear weapons-free zone explicitly covers the “Chagos Archipelago-Diego Garcia.” A footnote states that the territory appears on the map “without prejudice to the question of sovereignty.” However, the United Kingdom, United States, and France claim the footnote means the Chagos Archipelago is exempt.
Where does the dispute currently stand?
Almost 60 years after the detachment of Chagos, the United Kingdom still maintains its claim over the archipelago. London’s claim over the territory has been found to breach international law by the International Court of Justice, the U.N. General Assembly, and the International Tribunal for the Law of the Sea. However, regardless of widespread international opinion in favor of Mauritius, London has largely ignored these decisions.
In early 2023, the United Kingdom and Mauritius renewed negotiations to settle the Diego Garcia sovereignty dispute. Noting the significance of the U.S. base on Diego Garcia, Mauritius had previously offered the United States a 99-year lease on the island in exchange for full sovereignty over the Chagos Archipelago.
However, the offer included an explicit commitment that Mauritius support the “unhindered operation” of the U.S. military base, reviving outstanding questions about the inclusion of Diego Garcia in the African nuclear weapons-free zone.
The proposed lease thus raises an underlying tension in the sovereignty negotiations that challenges the principles of American and British nuclear nonproliferation. Under the current terms, the nuclear status of Diego Garcia must be settled before the sovereignty dispute can be addressed.
Last December, the U.K. dropped the negotiations, citing government concerns that ceding Chagos to Mauritius would endanger U.K. and U.S. defense interests in the Indo-Pacific. At present, the U.S. lease of Diego Garcia from the U.K. is set to expire in 2036.
What’s at stake?
Today, thousands of Chagossians live across Mauritius, the Seychelles, and the United Kingdom. Over the last few decades, they have continued to fight for reparations and their right to return. For former inhabitants of Chagos and their descendants, this dispute is about their dignity, heritage, and legacy.
For Mauritius, the push for sovereignty over Chagos builds on a larger trend of island states seeking to leave the British monarchy. Thus, the Diego Garcia dispute also presents an opportunity for the British government to rise to the occasion and set an important precedent for its approach to decolonization today.
As the leading architects of the prevailing international system, American and British disregard for international legal opinion repeatedly undermines the legitimacy of the international liberal order. Resolution of the Diego Garcia dispute could be a historic and strategic turning point for the narrative of great-power competition in the Indo-Pacific, but only if policymakers recognize it.
Diego Garcia has always been seen as a geopolitical asset for major global powers—whether as the subject of colonial competition, a stronghold against Soviet encroachment, a support facility for counterterrorism operations, a bulwark against China in the Indo-Pacific, or a platform for global deterrence.
Leaders of both the United States and the United Kingdom have come forward to assert their interests in preserving “a free and open Indo-Pacific” where governments can make their own choices. Policymakers must recognize that the Diego Garcia sovereignty negotiations are not a threat to these security interests but are instead an opportunity to bolster them.
The United States and United Kingdom can reinforce their Indo-Pacific security strategies by upholding international laws and norms while finding ways to fulfill their operational defense requirements. The two are not mutually exclusive.