Primer: The Chagos Archipelago Is Key to Resisting China’s Encroachments in the Indian Ocean
The status of the Chagos Archipelago, a small group of islands in the Indian Ocean, has recently become a newly relevant question of national security and defense strategy for both the United States and the United Kingdom. After Keir Starmer’s resignation as prime minister,1 his successor Andy Burnham has signaled a willingness to proceed with the plan of ceding the Chagos Archipelago in the British Indian Ocean Territory to the Republic of Mauritius.2 This would severely damage American power and influence in the Indian Ocean.
The Chagos Islands were a part of the British Mauritius Crown Colony until a few years before Mauritius gained independence in 1968. Britain separated Chagos from Mauritius to maintain a strategically significant air base that it could lease to the United States during the Cold War, effectively making the Diego Garcia air base a joint U.K.–U.S. installation.3 The base was vital for operations in the Gulf War,4 the conflicts in Afghanistan and Iraq,5 and numerous counterterrorism operations. It remains vital to long-range bombing capabilities and naval logistics in the Indian Ocean. The base allows U.K. and U.S. aircraft and ships to reach East Africa, the Persian Gulf, and South and Southeast Asia.6
Beginning in the 1980s, Mauritian sovereignty efforts intensified, and Mauritius has repeatedly insisted on regaining control of Chagos, despite the fact that the islands are over 1,250 miles away.7 In May 2025, after rulings and votes in 2019 from the International Court of Justice8 and the United Nations,9 respectively, mounted pressure on the United Kingdom to cede Chagos back to Mauritius, Starmer agreed and signed a deal with Mauritius to cede back formal sovereign control.10
The agreement effectively stipulates that the Republic of Mauritius is recognized as sovereign over the Chagos Archipelago, including over the island of Diego Garcia. The United Kingdom retains a lease on Navy Support Facility Diego Garcia for an initial ninety-nine years, allowing U.S. and U.K. naval and air operations to continue.11 In order to retain this lease on the naval base, the United Kingdom will pay annual installments of £165 million ($219.3 million) per year for the first three years of the lease and £120 million ($159.5 million) per year for years four through thirteen, and for the remainder of the ninety-nine-year period, the £120 million annual payment will be indexed to inflation. In addition, the United Kingdom will provide £45 million ($59.8 million) annually for twenty-five years for the economic development of Mauritius as well as a onetime £40 million ($53.2 million) payment to establish a fund for the benefit of the Chagossian community in Mauritius.12 Potential resettlement programs for Chagossians, 1,500 to 2,000 of whom had previously been expelled from the islands from 1968–73, will also be established.
Why Chagos Matters
The Chagos deal between the United Kingdom and Mauritius raises wider questions about sovereignty, international law, great-power competition, and the ability of democratic states to maintain strategic assets in an increasingly contested world. At the center of this debate is Diego Garcia, the largest island in the Chagos Archipelago and home to one of the United States and United Kingdom’s most important military facilities.
The island’s geographic position in the middle of the Indian Ocean gives it extraordinary strategic value, allowing allied forces to operate across a vast region stretching from the Middle East and East Africa to South Asia and the Indo-Pacific. In an era defined by renewed competition among major powers, supporters of maintaining British sovereignty argue that control of Diego Garcia is more important than at any time since the Cold War.13
The strategic importance of Diego Garcia comes from its location and its unique capabilities. Situated approximately halfway between Africa and Southeast Asia, the island provides a secure logistical hub for naval operations, long-range aviation, intelligence gathering, communications, and military resupply. During the Cold War, Diego Garcia became a critical Western outpost for monitoring Soviet naval activity in the Indian Ocean.14 Since then, its importance has increased as global trade routes, energy supplies, and maritime security have become increasingly contested. The base has supported operations connected to conflicts in the Middle East, including the Gulf War, operations in Afghanistan, and efforts to maintain freedom of navigation across critical maritime routes. For the United States, Diego Garcia represents a rare combination of geographic isolation, political reliability, and military utility.
In the future, the Indian Ocean will become a central arena of strategic competition because of China’s expanding naval presence, infrastructure investments, and diplomatic influence across the region.15 Beijing’s development of ports and strategic partnerships in countries such as Sri Lanka,16 Pakistan,17 and elsewhere has increased concerns among Western policymakers regarding China’s ability to establish a permanent military and economic presence along important maritime routes and within the same sphere as Diego Garcia.
Lack of Legal Rationale
The British government’s position on Chagos is a combination of humanitarian and legal concern18 and corruption.19 The British government under Starmer originally argued that Mauritius would be a reliable strategic partner and that a deal was needed to secure the long-term operation of the joint U.K.–U.S. base on Diego Garcia. But that is misleading. The Chagos deal is best understood not as a strategic necessity imposed by international law (which is customary and not mandatory), but as a political choice of a Labour government that is marred with corruption and risks weakening British sovereignty, complicating relations with allies, and setting a troubling precedent for the governance of other British Overseas Territories.
Nor is there legal compulsion to follow through any court ruling. The 2019 advisory opinion of the International Court of Justice, while politically influential, is not legally binding and does not impose a legal obligation on the United Kingdom to surrender the islands.20 The International Court of Justice cannot deliver a binding judgment between two states and does not automatically transfer sovereignty. The United Kingdom’s position has historically been that the Chagos Islands were lawfully administered as part of the British Indian Ocean Territory and that sovereignty remains a matter for political negotiation rather than automatic legal determination.21
The British Parliament has meanwhile abrogated its traditional constitutional role in the proposed U.K.–Mauritius agreement rather than simply allowing the treaty to pass, thereby harming a major foreign relationship of the U.K. government and creating uncertainty over the future operation of the joint U.K.–U.S. military base on Diego Garcia, including questions surrounding dispute resolution, military operations, nuclear weapons policy, and Mauritius’s wider foreign-policy relationships.
Any treaty provides only limited and largely unenforceable commitments regarding environmental protection and the welfare of displaced Chagossians, while potentially exposing the United Kingdom to new legal and diplomatic risks over the coming decades.
American Concerns
Fundamentally, however, the debate over the Chagos Archipelago is about American grand strategy in the Indian Ocean. Beyond any legal debate, Diego Garcia is one of the most important military facilities available to the United Kingdom and the United States, providing secure access to critical maritime chokepoints and supporting operations across the Indo-Pacific and Middle East.22 Transfer of sovereignty to Mauritius could create long-term uncertainty over the operation of the joint military base, particularly given Mauritius’s expanding relationship with China and Beijing’s growing economic and diplomatic influence throughout the Indian Ocean.
A further complicating factor is that Mauritius is a de facto Chinese ally and has expanded its campaign beyond diplomatic and international legal channels by introducing domestic legislation that attempts to influence speech and political activity outside its territory.23 In 2021, Mauritius enacted legislation relating to the protection of its territorial integrity, including provisions that critics argue could criminalize statements supporting competing claims over disputed territories, including the Chagos Islands, to potentially intimidate British officials, researchers, businesses, and members of the Chagossian community who express views contrary to the Mauritian position.24 Mauritian law makes it a criminal offense to “misrepresent” Mauritius’s sovereignty over any part of its claimed territory, including the Chagos Islands.
The potential danger of increased Chinese influence in the area of Chagos would unnecessarily complicate allied military planning and reduce strategic flexibility at a time when regional security challenges are intensifying.25 While Mauritius may currently provide assurances regarding Diego Garcia, international relationships can change over decades, and strategic facilities require long-term certainty rather than temporary guarantees.26
Potential American Actions
President Donald Trump recently came out strongly against the agreement.27 His main criticism was that it potentially jeopardizes U.S. military operations in the area and gives the archipelago to Mauritius, a small nation with historical economic ties to China and Iran. Jonathan Powell, Starmer’s national security adviser (whom Burnham has signaled he may keep on in his own cabinet)28 and the lead British negotiator for the agreement,29 has rebuffed the concerns of there being a “Chinese base,” arguing that the agreement prohibits one.30
But this response does not address concerns about how China may exert influence in the region in other ways, whether through investment, diplomacy, or Mauritius’ debts to China. Further, future Mauritian governments may increase the republic’s reliance on China. Powell himself has ties to China that have proven controversial. In his capacity as both a private citizen and a government official, he has been criticized for having an overly accommodating attitude toward China.31 He has professional contacts in Beijing and has been accused of interfering with an investigation into two British officials who were found to be spying for China.32
In June 2026, the Trump administration explored the possibility of buying Chagos,33 but when Mauritius learned of the idea, it claimed that its sovereignty over Chagos is non-negotiable.34 This does not necessarily exclude the option in the future. Possibilities could include waiting until the U.K.–Mauritius agreement is complete and then either arranging for direct American control over the airbase or outright acquiring American sovereignty over the Chagos Archipelago through an effective purchase of the islands from Mauritius. The United States may also continue to exert pressure on the United Kingdom to retain its sovereignty in order to maintain the status quo of the Diego Garcia base.
The Chagos Archipelago occupies a position of exceptional importance, and any political arrangement that creates opportunities for Chinese intelligence collection, economic leverage, or military influence over the surrounding islands would represent an unacceptable risk to American national security. Washington should insist upon legally binding security guarantees, robust inspection mechanisms, and long-term restrictions preventing any Chinese military, intelligence, or dual-use presence anywhere within the archipelago. Should such safeguards prove unattainable, the United States should be prepared to negotiate a structured arrangement granting it direct sovereignty or long-term administration over the islands in order to secure Diego Garcia and preserve freedom of operations. In the most extreme contingency, the United States should consider the outright seizure of the islands to ensure uninterrupted control of a strategically indispensable military hub, similar to the strategic logic that historically underpinned U.S. intervention in Panama and the protection of the Panama Canal.
Conclusion
The proposed agreement illustrates a broader tension, and in some respects a direct conflict, between the sovereignty claims advanced through postcolonial decolonization narratives and the enduring strategic imperatives of major powers such as the United States and the United Kingdom. This tension is particularly pronounced in the Indo-Pacific, where intensifying geopolitical competition has elevated the strategic value of military infrastructure and forward basing arrangements.
The United Kingdom, given its long-standing commitment to the principles of a rules-based international order, has faced considerable diplomatic and legal pressure from both the United Nations and the International Court of Justice to address the status of the Chagos Archipelago. Nevertheless, neither institution possesses the legal authority to compel the United Kingdom to conclude or implement the proposed agreement.
Despite the absence of a binding legal obligation, political considerations make it likely that the agreement will proceed. Consequently, the United States must focus less on the unresolved question of sovereignty than on the assurance of the long-term integrity, security, and operational effectiveness of the Navy Support Facility Diego Garcia.
The preservation of Diego Garcia should remain the central strategic objective. The installation constitutes a critical component of the United States’ military posture, providing indispensable logistical, intelligence, and operational support for missions spanning the Middle East, East Africa, and the wider Indo-Pacific. Its continued availability is therefore essential to maintaining American power projection and regional deterrence. Although the agreement is intended to preclude any direct Chinese military involvement, the People’s Republic of China cannot be treated as an irrelevant actor.
Beijing’s sustained efforts to expand its military presence and strategic influence throughout the Indian Ocean require careful consideration of the agreement’s long-term implications. These concerns are further reinforced by perceptions that the lead British negotiator is soft on China. While such perceptions should not substitute for evidence, they underscore the need for rigorous safeguards to ensure that no aspect of the agreement compromises the operational security or strategic value of the Diego Garcia facility.
Endnotes
1. Kevin Shalvey, “UK Prime Minister Keir Starmer Announces Resignation with ‘Good Grace,’” ABC News, June 22, 2026, https://abcnews.com/International/uk-prime-minister-keir-starmer-resign/story?id=134087581.
2. Katie Harris, “Fears Andy Burnham Will Push Ahead with Chagos Deal as Weak as Keir Starmer,” Daily Express, July 6, 2026, https://www.msn.com/en-gb/news/other/fears-andy-burnham-will-push-ahead-with-chagos-deal-as-weak-as-keir-starmer/ar-AA27jKPc.
3. U.S. Navy, “History,” Naval Support Facility Diego Garcia, accessed July 10, 2026, https://cnrj.cnic.navy.mil/Installations/NSF-Diego-Garcia/About/History/.
4. Richard Edis, Peak of Limuria: The Story of Diego Garcia and the Chagos Archipelago (Chagos Conservation Trust, 2004), 94.
5. Marine Corps Institute, Afghanistan: An Introduction to the Country and People ( Marine Corps Institute, 2003), 27, https://www.govinfo.gov/content/pkg/GOVPUB-D214-PURL-LPS58082/pdf/GOVPUB-D214-PURL-LPS58082.pdf.
6. Jill Lawless, “What to Know About Diego Garcia After Iran Targets the Remote Island’s Key U.S. Military Base,” Associated Press, March 21, 2026, https://apnews.com/article/diego-garcia-iran-missiles-what-to-know-d51bd9c3bcd83ee0300288221bff5614.
7. International Court of Justice, “Written Statement of Australia,” Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965: Advisory Opinion of 25 February 2019 (International Court of Justice, 2019), para. 12, https://www.icj-cij.org/node/105657.
8. International Court of Justice, Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965: Advisory Opinion of 25 February 2019 (International Court of Justice, 2019), https://www.icj-cij.org/node/105778.
9. United Nations General Assembly, Advisory Opinion of the International Court of Justice on the Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965: Report of the Secretary-General, A/74/834 (United Nations, 2020), https://digitallibrary.un.org/record/3806313?utm=&v=pdf.
10. PA News Agency, “Starmer Signs Deal with Mauritius to Hand Chagos Islands,” Times and Star, May 22, 2025, https://www.timesandstar.co.uk/news/national/25184859.starmer-signs-deal-mauritius-hand-chagos-islands/.
11. Government of the United Kingdom and Government of the Republic of Mauritius, Agreement Between the Government of the United Kingdom of Great Britain and Northern Ireland and the Government of the Republic of Mauritius Concerning the Chagos Archipelago Including Diego Garcia, Mauritius No. 1 (2025), CP 1334 (Foreign, Commonwealth and Development Office, 2025), 8, https://assets.publishing.service.gov.uk/media/682f25afc054883884bff42a/CS_Mauritius_1.2025_Agreement_Chagos_Diego_Garcia.pdf.
12. Ibid., 33–35.
13. Nitya Labh, “US Military Base on Diego Garcia: What Is Its Strategic Importance?,” Chatham House, February 19, 2026, https://www.chathamhouse.org/2026/02/us-military-base-diego-garcia-what-its-strategic-importance.
14. John M. Crewdson, “Senate Approves Indian Ocean Base; Mansfield Resolution Against It Fails,” The New York Times, July 29, 1975, https://www.nytimes.com/1975/07/29/archives/senate-approves-indian-ocean-base-mansfield-resolution-against.html.
15. Darshana M. Baruah, Rupert Schulenburg, Viraj Solanki, and Erik Green, “China in the Indian Ocean: A Stronger Indo-Pacific Presence,” International Institute for Strategic Studies Charting China, May 22, 2025, https://www.iiss.org/charting-china/2025/05/china-in-the-indian-ocean-a-stronger-indo-pacific-presence/.
16. Ministry of Foreign Affairs of the People’s Republic of China, “Joint Statement Between the People’s Republic of China and the Democratic Socialist Republic of Sri Lanka,” Ministry of Foreign Affairs of the People’s Republic of China, January 16, 2025, https://www.mfa.gov.cn/eng/xw/zyxw/202501/t20250116_11536637.html.
17. Embassy of the People’s Republic of China in the Islamic Republic of Pakistan, “Joint Statement Between the People’s Republic of China and the Islamic Republic of Pakistan,” Embassy of the People’s Republic of China in Pakistan, May 26, 2026, https://pk.china-embassy.gov.cn/eng/zbgx/202605/t20260528_11919306.htm.
18. Patrick Christys, “Keir Starmer’s Chagos Deal: Human Rights Body Takes on Former Human Rights Lawyer,” GB News, June 7, 2025, https://www.gbnews.com/politics/keir-starmer-chagos-deal-human-rights-body-takes-on-former-human-rights-lawyer.
19. Ben Lazarus, “Starmer’s Friend Made Millions from Chagos Deal,” The Daily Telegraph, February 17, 2026, https://www.telegraph.co.uk/politics/2026/02/17/starmers-friend-made-millions-from-chagos-deal/.
20. Yuan Yi Zhu, “A Real Decolonisation Dispute,” The Critic, May 2023, https://thecritic.co.uk/issues/may-2023/a-real-decolonisation-dispute.
21. United Kingdom of Great Britain and Northern Ireland, Written Statement of the United Kingdom, Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965 (Request for Advisory Opinion), International Court of Justice, February 15, 2018, 8–9, https://www.icj-cij.org/sites/default/files/case-related/169/169-20180215-WRI-01-00-EN.pdf.
22. Labh, “US Military Base on Diego Garcia.”
23. Ministry of Foreign Affairs of the People’s Republic of China, “China and Mauritius,” Ministry of Foreign Affairs of the People’s Republic of China, accessed July 10, 2026, https://www.fmprc.gov.cn/mfa_eng/gjhdq_665435/2913_665441/3039_664104/.
24. Yuan Yi Zhu, Intimidation as Foreign Policy: How Mauritius Has Attempted to Criminalise UK Sovereignty over the Chagos Islands (Policy Exchange, January 29, 2024), https://policyexchange.org.uk/publication/intimidation-as-foreign-policy/.
25. Cabinet Office, National Security Strategy 2025: Security for the British People in a Dangerous World, CP 1338 (Cabinet Office, 2025), para. 15, https://www.gov.uk/government/publications/national-security-strategy-2025-security-for-the-british-people-in-a-dangerous-world/national-security-strategy-2025-security-for-the-british-people-in-a-dangerous-world-html.
26. Prime Minister’s Office, Republic of Mauritius, “Prime Minister Holds Press Conference on Agreement between Mauritius and UK on the Chagos Archipelago,” The Prime Minister, May 26, 2025, https://primeminister.govmu.org/pm/?p=1975.
27. Donald J. Trump, “I have been telling Prime Minister Keir Starmer, of the United Kingdom, that Leases are no good,” Truth Social, February 18, 2026, https://truthsocial.com/@realDonaldTrump/posts/116093101641103750.
28. Reuters, “UK PM-in-Waiting Vows to Rebuild ‘Hard Power’ for More Dangerous World,” Reuters, July 9, 2026, https://www.reuters.com/world/uk/uk-pm-in-waiting-vows-rebuild-hard-power-more-dangerous-world-2026-07-09/.
29. Foreign, Commonwealth and Development Office, “Jonathan Powell Appointed as Special Envoy for BIOT Negotiations,” Gov.UK, September 6, 2024, https://www.gov.uk/government/news/jonathan-powell-appointed-as-special-envoy-for-biot-negotiations.
30. Sian Baldwin, “What Is the Chagos Islands Deal? Proposals Fall Apart at the Eleventh Hour,” Yahoo News UK, April 13, 2026, https://uk.news.yahoo.com/where-chagos-islands-why-uk-130507303.html.
31. Oliver Wright, “Jonathan Powell: National Security Adviser with More Than China to Worry About,” The Times, October 12, 2025, https://www.thetimes.com/uk/politics/article/jonathan-powell-national-security-adviser-r6x3m09j9.
32. Oliver Wright, “Keir Starmer’s Security Adviser ‘Too Close to China’, Ministers Warn,” The Times, October 10, 2025, https://www.thetimes.com/uk/politics/article/jonathan-powell-china-keir-starmer-aide-llr5fbfvk.
33. Reuters, “US Considers Buying Chagos Islands, Telegraph Reports,” Investing.com, June 7, 2026, https://www.investing.com/news/world-news/us-considers-buying-chagos-islands-telegraph-reports-4729686.
34. Reuters, “Mauritius Has Not Received US Proposal on Chagos Islands,” Investing.com, June 8, 2026, https://www.investing.com/news/world-news/mauritius-has-not-received-us-proposal-on-chagos-islands-4729937.
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