A Footprint of Unfreedom: The Future of Naval Support Facility Diego Garcia

For over 50 years, the United States has maintained a military base on Diego Garcia, the largest island of the Chagos Archipelago in the central Indian Ocean.¹ The United Kingdom (UK) governs Diego Garcia and the rest of the Chagos Islands as the British Indian Ocean Territory (BIOT), a colonial jurisdiction created in 1965 for the sole purpose of facilitating the militarization of Diego Garcia.² In February 2019, the International Court of Justice (ICJ) ruled in an advisory opinion that the UK’s occupation of the Chagos Islands is illegal under international law and that the islands rightfully belong under Mauritian sovereign control.³ The ICJ further advised that all members of the United Nations (UN) are obligated to work toward the decolonization of Chagos. Three months later, 116 states voted in the UN General Assembly (UNGA) to endorse the ICJ’s decision and call upon the UK government to transfer the Chagos Archipelago to Mauritius. Only four states joined with the UK and United States to oppose the resolution.⁴

What do these legal and political developments mean for the future of UK sovereignty over the Chagos Islands? What are the implications for the continued use of Diego Garcia by the US military? Because London has been dedicated to governing the BIOT in a way that privileges the military interests of the United States, it has long been assumed that continued UK sovereignty over Chagos is critical to the success of Naval Support Facility Diego Garcia. In what follows, I challenge this conventional wisdom to argue that the ICJ’s ruling, the UNGA vote, and other related developments show that UK control has become an unnecessary strategic liability for the United States. I argue that the historical (colonial) origins of the BIOT as a discrete administrative unit have encumbered the territory with some damaging political pathologies. These problems cannot be remedied by decision makers in London or Washington and will only worsen over time.⁵ I conclude that the United States should now back Mauritian sovereignty over the Chagos Islands—not only because supporting decolonization is the ethical and legally required thing to do (although these motivations ought to weigh heavily on US decision makers) but also because there is a hardheaded strategic rationale for preferring Port Louis over London as a landlord.

To be sure, there will be costs to the United States if Diego Garcia and the rest of the Chagos Islands come under Mauritian control. Namely, the archipelago would no longer be contained within a jurisdiction purpose-built for the conduct of US military operations (as is the case with the BIOT). It will take careful diplomatic work to ensure that the transition from UK to Mauritian sovereignty does not impose new burdens upon Naval Support Facility Diego Garcia. However, as I describe below, even the UK government recognizes that Mauritius will assume control over the Chagos Islands at some point—an undertaking that is binding upon the UK under international law. There is even a nontrivial possibility that the UK could initiate a handover of sovereign authority to Mauritius without US consent. Combined with mounting international pressure for decolonization, these political uncertainties create a strong rationale for the United States to acknowledge Mauritius’s claims sooner rather than later with a view toward securing an enduring say over the future of the territory. To do otherwise would be to risk being overtaken by events and perhaps losing access to Diego Garcia altogether.

Background: Political Pathologies in Britain’s Last Colony

The island of Diego Garcia was first identified as the potential site of a US military base in the 1950s, in the context of the intensifying Cold War between the United States and the Soviet Union.⁶ Serious discussions over the creation of a base began in the early 1960s, with the United Kingdom and United States signing a formal agreement to open up the territory for military purposes in 1966.⁷ Construction began in March 1971, and just two years later Diego Garcia was home to a fully operational communications facility charged with monitoring Soviet naval activity in the Indian Ocean.⁸ Over the course of the 1970s and 1980s, a series of geopolitical events—especially the Iranian Revolution and the Soviet invasion of Afghanistan—prompted the United States to greatly expand the base. The island’s lagoon was dredged to create a ship channel, turning basin, and berthing space for warships, and its runway and hangar space were expanded.⁹ By the end of the 1980s, Diego Garcia had become a vital hub for pre-positioned air and naval forces in the Indian Ocean region. The base played key roles in the First Gulf War (1990–1991), Operation Desert Fox (1998), and the post–9/11 invasions of Afghanistan (2001) and Iraq (2003).

Naval Support Facility Diego Garcia has been a successful military base for two main reasons. Geographically, the island of Diego Garcia occupies a strategically valuable location in the center of the Indian Ocean—almost exactly equidistant between the east coast of Africa and the Indonesian island of Aceh, making it indispensable as a staging post for operations in the entire Indian Ocean region—and boasts natural features that make it capable of hosting large numbers of naval vessels and aircraft.¹⁰ Just as important as its geostrategic assets is the island’s unique political situation: the BIOT is the only fully discrete (albeit nonsovereign) territorial jurisdiction in the world to have been created for the sole and explicit purpose of housing a military base. Up until 1965, Diego Garcia and the rest of the Chagos Archipelago had been part of the UK-controlled Crown Colony of Mauritius. At the Lancaster House Constitutional Conference in September 1965, however, UK officials convinced a delegation of Mauritian independence leaders to allow the British Empire to retain control over the Chagos Archipelago even after Mauritius became a fully sovereign state. The UK’s negotiators acknowledged that the islands would be returned to Mauritian control once they were no longer required by the United Kingdom (and, by extension, the United States) for military purposes.¹¹ Weeks later, Queen Elizabeth II approved an order in council to create the BIOT—a new jurisdiction and the last colony ever created by the British Empire.¹² Mauritius duly obtained its independence in 1968 without the Chagos Archipelago as part of its internationally recognized territory.

The reason for excising Chagos from the Crown Colony of Mauritius to form the new Crown Colony of BIOT was that both London and Washington wanted to avoid a situation where any new military base would be dependent upon a postcolonial landlord.¹³ If the archipelago had remained part of Mauritius and had thus been under the sovereign authority of Port Louis from 1968 onward, the concern among American strategists was that the territory might easily come under the sway of communist or otherwise anti-US groups. These were reasonable fears: numerous postcolonial states in Africa and Asia took anti-US positions in the Cold War era, with some, such as Iran, switching from being stalwart US allies to implacable adversaries. In the mid-1960s, nobody in London or Washington could be sure that Mauritius would remain tightly aligned with the United Kingdom and United States after it gained independence. Given these geopolitical uncertainties, keeping the Chagos Archipelago under the direct control of the UK government was viewed as a prudent way to provide the United States with guaranteed long-term access to Diego Garcia—effectively creating a legal-political umbrella beneath which the islands would be sheltered from the vicissitudes of postcolonial and anti-imperialist politics.

In the event, the BIOT’s creation did not provide as clean a break with Mauritius as strategic planners in London and Washington had anticipated. In 1980, the government of Mauritius formally laid claim to Chagos on the basis that, when the BIOT was created, prevailing international law had prohibited colonizers from carving up their existing imperial possessions into new jurisdictions.¹⁴ In 1983, a select committee of Mauritian parliamentarians further concluded that their country’s leaders prior to independence had been under duress when they agreed at Lancaster House to the excision of Chagos.¹⁵ From this view, the separation of Chagos from Mauritius had been improper and should be regarded as an ongoing violation of international law—an argument subsequently endorsed by international political bodies such as the Organization for African Unity, the African Union, and the UNGA before being confirmed by the ICJ’s advisory opinion in February 2019.¹⁶ Every Mauritian leader since the early 1980s has made it clear that Chagos is an integral part of Mauritius—a commitment enshrined in the country’s constitution—placing considerable strain on Mauritius’s bilateral ties with both the United Kingdom and United States.

Archival documents show that UK diplomats in the 1960s knew full well that excising Chagos from Mauritius was in violation of international rules and, if not done carefully, would draw unwanted scrutiny from the UN’s Special Committee on Decolonization (“Committee of 24”).¹⁷ However, violating the territorial integrity of Mauritius was hardly the worst crime knowingly perpetrated by British officials as part of the creation of the BIOT. Between 1965 and 1973, around 1,500 indigenous Chagos Islanders were forcibly expelled from their homes to satisfy the needs of Diego Garcia’s new military occupants.¹⁸ The islanders were misrepresented to external audiences as migrant laborers, despite the authorities’ clear knowledge that many Chagossian families had lived on the islands for generations. The rationale for the expulsions was that the Chagos Islands had to be made rid of a permanent population if they were to play host to a US military base. As one UK official wrote: “We must surely be very tough about this. The object of the exercise is to get some rocks which will remain ours. There will be no indigenous population except seagulls who have not yet got a committee (the Status of Women Committee does not cover the rights of birds).”¹⁹

The Chagossians never acquiesced in their exile. They fought back—protesting vigorously in both Mauritius and the United Kingdom.²⁰ These efforts produced some important victories: financial compensation from the UK government,²¹ recognition of UK citizenship (and thus the ability to migrate onward to the United Kingdom),²² and even—if only briefly—the technical right to return to the Chagos Islands (discussed in more detail below). In Mauritius, the left-wing political parties Lalit and Mouvement Miliant Mauricien made the Chagossians’ plight part of their electoral platforms. The fate of the islanders even became an issue in US domestic politics for a brief time, with lawmakers in the House of Representatives raising the issue of the islanders’ mistreatment during a 1975 hearing on whether to expand the base on Diego Garcia.²³

In the United Kingdom, the Chagossians’ cause has never been a high-profile political issue—but neither has it been entirely buried. In the late 1970s and 1980s, left-wing members of the Labour Party such as Tam Dalyell and Robin Cook made intermittent efforts to raise the issue with government ministers. Beginning in the late 1990s and early 2000s, a larger number of parliamentarians began to work together to support the islanders—eventually coming together to form the All-Party Parliamentary Group on the Chagos Islands in 2008.²⁴ Between 2010 and 2015, the Chagossians could even count several members of the UK Cabinet as (at least nominal) supporters of their right of return—including Deputy Prime Minister Nick Clegg. In 2015, a longtime ally of the Chagossians—Jeremy Corbyn—became leader of the Labour Party and thus leader of the official opposition in Westminster. Corbyn has continued to speak out in favor of the Chagossians since becoming the UK’s nominal prime minister in waiting.

Up until now, no amount of campaigning by Mauritius, the Chagossians, or their supporters has been enough to shake UK political control over Chagos. Officials in London admit that the expulsion of the Chagos Islanders was regrettable and even illegal in its original manner of execution but always couple their professions of contrition with the twin insistences that (1) the islands will revert to Mauritian control once they are no longer needed for military purposes but will be treated as sovereign UK territory until that time; and (2) the current ordinances preventing the islanders’ return to Chagos are legal and, in any case, resettlement of the archipelago would be prohibitively costly.²⁵

London as Landlord: Diminishing Returns, Emerging Threats

The sole purpose of the BIOT’s creation was to furnish London and Washington with a territory that could be made exclusively available for military purposes. Judged against this criterion, the BIOT has been a resounding success. The United Kingdom has ensured that there is no permanent civilian population in the Chagos Islands (thus, no representative government and no adjacent communities to accommodate), provides little meaningful oversight of US military activities, and extends few laws to the jurisdiction. As Peter H. Sand has argued, Diego Garcia is essentially a “legal black hole” in the Indian Ocean—the perfect place for a military base to exist in near-total seclusion.²⁶ Moreover, the United Kingdom does not charge rent for the base.²⁷ For all these reasons, Anglo–American cooperation over Diego Garcia can be judged to have been a worthwhile arrangement from the perspective of the United States.

Governing the BIOT in service of US interests has required the UK government to be active along two fronts: (1) to oppose Mauritius’s claims to sovereignty; and (2) to oppose the exiled Chagossians’ fight for a right to return to the islands. For a long time, Whitehall found itself busiest on the second of these fronts. As already mentioned, the Chagossian community won a High Court victory in 2000 that technically restored their right to return in UK law.²⁸ At the time, the UK foreign secretary was Robin Cook—a longtime supporter of the Chagossians since his days as a backbench Labour MP. After losing to the islanders before the High Court, Cook undertook on behalf of the UK government to accept the ruling in full and investigate the possibility of facilitating a return to the outer Chagos Islands (that is, those islands other than Diego Garcia).²⁹ It was not until 2004, in the aftermath of the invasion of Iraq, that Cook’s successor, Jack Straw, used new orders in council to exile the islanders afresh. These legal instruments—a form of primary legislation made by UK ministers using royal prerogative³⁰ rather than a piece of legislation promulgated by the BIOT commissioner—had to be defended in court against robust challenges from the Chagossians and their lawyers, resulting in eight years of litigation that cost the British taxpayer millions of pounds and placed a bright spotlight on the US military’s activities on Diego Garcia.³¹

Fighting to keep the Chagossians in exile was a public relations disaster for the UK government. Human rights groups and news organizations have been scathing in their coverage. One of the first in-depth reports into the territory was published in 1982 by the Minority Rights Group, which excoriated the UK government for its failure to uphold the Chagossians’ rights despite being willing to wage war against Argentina in defense of the Falkland Islanders.³² Two decades later, the investigative journalist John Pilger produced a TV documentary (Stealing a Nation) to chronicle the Chagossians’ story. In 2008, activists from Greenpeace tried to land on Diego Garcia to protest the islanders’ treatment.³³

Also in 2008, the UK government was forced to admit that Diego Garcia had been used by the US military for extraordinary rendition flights—despite having earlier assured Parliament that no such flights had visited the territory.³⁴ This admission fueled a string of allegations that the United Kingdom had made itself complicit in the operation of a Central Intelligence Agency (CIA) “black site” on Diego Garcia.³⁵ And in 2010, the news media reported that the UK government had “manipulated” the results of a 2002 feasibility study into resettlement of the Chagos Islands in an attempt to stymie the efforts of the exiled islanders to return home.³⁶ Taken together, these two developments—reports of a CIA detention facility and allegations that the UK government was using underhand methods to keep the Chagos Islanders in exiled—gave rise to the impression that the Chagossians’ mistreatment was entirely at the behest of a US government intent on using Diego Garcia for shadowy purposes. It did not help that, some years later, UK officials were accused of lying about the availability of flight logs pertaining to Diego Garcia.³⁷

Even withstanding this torrent of negative publicity, it still could be argued that the BIOT administration provided the United States with a relatively secure political unit within which to house its base on Diego Garcia. However, from 2010 onward, even this advantage of the BIOT framework began to unravel after London decided to create a Marine Protected Area (MPA) in the Chagos Archipelago. An international coalition of conservationist organizations including Pew Environment first put forward the idea of creating an MPA in Chagos was in 2009.³⁸ The UK government, especially Foreign Secretary David Miliband, warmly welcomed the proposal, partly because politicians like Miliband wanted to secure a “green legacy” for themselves and partly because officials believed that a new layer of environmental protections in the Chagos Archipelago would constitute an additional barrier to the islanders’ return.³⁹ Mauritius and most major Chagossian organizations argued against the creation of the MPA—or at least, argued for a greater say in its formation and management. However, in April 2010 (on a day that the UK Parliament was in recess), the Foreign and Commonwealth Office announced that it had decided to designate an MPA in the Chagos Islands. At the time, it was the largest MPA of its kind in the world—a (green) feather in the cap of Miliband and the outgoing Labour prime minister, Gordon Brown.

The creation of a formal MPA in Chagos created new legal and political opportunities for Mauritius and the Chagossians to press their interests against the UK government. For their part, the Chagossians leveraged WikiLeaks-released diplomatic cables (which suggested that the creation of the MPA had been done cynically to thwart the islanders’ hopes of resettlement) to request a judicial review of the MPA decision.⁴⁰ This effort ultimately failed to overturn the MPA’s creation—although it went all the way to the UK Supreme Court. At the same time, Mauritius lodged formal protests with the UK government that the manner of the MPA’s creation had violated its rights pertaining to the BIOT, including certain legal rights deriving from the UN Convention on the Law of the Sea (UNCLOS). Finding its diplomatic overtures rebuffed by London, Port Louis opted to take its case to the Permanent Court of Arbitration (PCA) in The Hague, which has jurisdiction to rule on disputes arising from states’ participation in the UNCLOS regime.

Contrary to the wishes of the UK government, the PCA decided to hear Mauritius’s arguments and, in 2015, an arbitral tribunal ruled in a binding decision that the manner of the MPA’s creation had indeed contravened international law.⁴¹ Among other things, the PCA held that Mauritius should have been afforded more of a say in the creation of the MPA because of its abiding interest in the governance of the territory, which stems from the repeated undertakings given by the UK government that Mauritius will, one day, be awarded sovereignty over the islands. The ruling thus established in public international law that Mauritius must be consulted on issues concerning the future governance of the islands—not just when it comes to marine conservation, but on other matters too. The UK government seems to have accepted these findings, subsequently arguing before the UNGA that “we acknowledge Mauritius’s long-term interest in the archipelago” and “we [have] offered . . . a framework for the joint management, in environment and scientific study, of all the islands of the territory except for Diego Garcia.”⁴² In other words, the United Kingdom has accepted in light of the PCA decision that its sovereignty over the Chagos Archipelago is not absolute and that consultations with Mauritius are an international legal requirement going forward. This is a consequential development, which calls into question London’s ability to govern the islands without interference from Mauritius. It was also an entirely unforced error—the biggest sign yet that UK sovereignty over Chagos will not always be exercised in ways conducive to US interests.

The ICJ’s advisory opinion in February 2019 was even worse for the UK government. Having become frustrated with the UK government’s handling of its claims to Chagos in the wake of the PCA decision, the government of Mauritius decided in 2017 that it would seek an advisory opinion from the World Court on the question of sovereignty. As per UN rules, Port Louis formally requested that the UNGA refer the matter to the ICJ. In June 2017, the General Assembly approved Mauritius’s motion by an overwhelming majority. The United Kingdom lobbied hard to prevent the matter from coming before the ICJ, but, when the question of a referral came to be voted upon, London could not even count on the support of most European Union member states—a telling indictment of the United Kingdom’s declining influence in the world.⁴³ That the UK government could not stop the case being referred to the ICJ was a powerful demonstration of how little diplomatic clout London can muster in defense of UK national interests. That the United Kingdom lost the ensuing case just served to compound the humiliation. For even though the ICJ’s ruling was not binding, its decision was unambiguous and damning: that UK control over the Chagos Islands has been illegal under international law ever since 1965 and should be brought to a swift end.

One major implication of the ICJ ruling is that the World Court has now formally advised that every UN member, including the United States, has an obligation to decolonize Chagos. Before February 2019, the United States has been able to hide behind the fig leaf of insisting that the question of sovereignty over Chagos was a purely bilateral matter to be decided between the United Kingdom and Mauritius. This position was never entirely watertight, but it helped to shift international attention away from the base on Diego Garcia.⁴⁴ Now, however, the ICJ has articulated a powerful legal reality that, in fact, the continued colonization of the BIOT is an offense against all—including the United States. This is a difficult recommendation for the US government to dismiss altogether.

Thanks to decisions rendered by the PCA, ICJ, and UNGA, the legal and ethical reasons for decolonizing Chagos are plain to see. However, as argued here, there is also a compelling pragmatic reason for why the United States (and its military planners in particular) should support decolonization. In short, the political and legal status quo in the BIOT is becoming unsustainable. On the one hand, the PCA’s ruling concerning the Chagos MPA has made it clear that Mauritius has an actionable interest in the territory and must be consulted over major changes to the governance of the BIOT—a set of legal rights that the United Kingdom has accepted, and which could later be pressed in ways that neither London nor Washington approve of. On the other hand, the ICJ has leveraged some clear rules on decolonization to show that the United Kingdom should not be in Diego Garcia in the first place and that the BIOT should cease to exist as a jurisdiction. Meanwhile, an overwhelming majority of the world’s states have expressed a view to concur with the ICJ’s advisory opinion that Mauritius is the legitimate sovereign power in the Chagos Archipelago. In short, UK sovereignty is being squeezed. In the eyes of American strategists, at what point does London’s stewardship of the islands start to look like a strategic liability?

In addition to these international threats to the political status quo in the BIOT, there is also a domestic threat emanating from the United Kingdom that warrants mentioning. As noted above, the current leader of the official opposition, Jeremy Corbyn, is a longstanding and outspoken supporter of the Chagos Islanders.⁴⁵ He could easily become a future UK prime minister. Such a premiership would constitute an existential threat to the BIOT. In April 2019, Corbyn wrote to Prime Minister Theresa May to condemn her decision to ignore both the ICJ ruling and the UNGA resolution on the status of the BIOT.⁴⁶ The implication of Corbyn’s letter was that he supported Mauritius’s demands that the BIOT be decolonized—a position in keeping with his longstanding record on the issue. This suggests that, if he ever became prime minister, Corbyn might voluntarily initiate the process of ceding the Chagos Archipelago to Mauritius. Other plausible options would be for Corbyn to submit the issue to a binding arbitration by the ICJ or to simply authorize the resettlement of the islands under UK supervision.⁴⁷ And as prime minister, Corbyn could implement any of these scenarios via the exercise of royal prerogative powers. He would not require any new legislation—or even the agreement of the United States.

Even if Corbyn never becomes prime minister, it must now be regarded as at least feasible that some other future leader could choose to relinquish UK sovereignty over Chagos or else initiate a resettlement over and above the objections of the United States. Indeed, a restoration of the Chagos Islanders’ right of return seemed entirely possible during the 2010–2015 coalition government of Conservatives and Liberal Democrats. In September 2010, the Business Secretary Vince Cable even released a letter to announce that the government had agreed to allow resettlement to proceed.⁴⁸ The information contained within the letter turned out to be an inaccurate reflection of government policy, but the bizarre circumstances surrounding its release were nevertheless suggestive of a high level of support enjoyed by the Chagossians in the cabinet at that time.

The bottom line is that the United Kingdom can no longer be considered the reliable landlord it once was in Chagos. Its political leaders cannot be trusted to indefinitely toe the line for the United States—especially when they incur significant embarrassment from doing so but without any discernible benefits in return. How long will it be before a government in London decides that the legal, political, and ethical problems associated with the BIOT are too serious to ignore? What will happen if the United Kingdom decides to initiate the transfer of sovereign control to Mauritius before the United States has had an opportunity to plan for a change in ownership?⁴⁹ It makes strategic sense for the United States to avoid the grave uncertainties bound up with these questions by simply choosing of its own violation to opt for Mauritian sovereignty.

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(US Navy photo by Ensign Victor Obando)

Figure 1. Infrastructure improvements. US Navy Seabees deployed with Naval Mobile Construction Battalion (NMCB) 5’s Detail Diego Garcia work with civilian contractors during a concrete placement that will form a pad for the foundation for a tension fabric structure in support of the US Air Force. NMCB-5 is deployed across the Indo-Pacific region, conducting high-quality construction to support US and partner nations to strengthen partnerships, deter aggression, and enable expeditionary logistics and power projection.

After Decolonization: Looking to the Future

The United States does not have a direct say over who controls the Chagos Islands—nor should it. However, Washington does have a powerful indirect say. As already discussed, the UK government’s position is that it will cede the islands to Mauritius upon such a time as they are no longer needed for defense and security purposes. And because the US base on Diego Garcia is the only means by which any of the Chagos Islands are used for such purposes, it follows that the United Kingdom will relinquish sovereignty over the archipelago as soon as the United States offers its acquiescence. At least, there would be no reason for London to object to Mauritian sovereignty over Chagos if it was something that the United States supported.

I have suggested that the United States should use its leverage to bring about the transfer of sovereignty to Mauritius. The obvious objection to this proposal is that Mauritian sovereignty might prove to be more of a constraint on US military activities than the BIOT regime has been. This is a reasonable objection. It is difficult to imagine any political ordering that could be more favorable to the US military than that which has been provided by the BIOT—not even US sovereignty over the islands. However, the supposed drawbacks of full Mauritian control over Chagos can be managed if US leaders show foresight. And in any case, the BIOT is already showing signs of collapse. The jurisdiction belongs to a different era and cannot be expected to last forever. My argument is that decision makers in Washington would be best served by accepting the inevitable and shifting their focus toward working with Mauritius to forge a long-term understanding about the US presence on Diego Garcia.

How should the United States seek to shape the future of Diego Garcia and the rest of the Chagos Islands? There are several available options. One possibility would be to encourage London and Port Louis to agree upon a phased transfer of sovereignty over the Chagos Archipelago, beginning with the so-called outer Chagos Islands. After all, most of the islets in the Chagos Archipelago are more than 100 miles away from Diego Garcia. None of this land has ever been used for defense and security purposes and so, even by UK standards, it should be transferred to Mauritius.

It would not be the first time that the BIOT has been dismembered in such a way. At the time of the BIOT’s creation in 1965, it comprised not just the Chagos Archipelago but also the island groups of Farquhar, Aldabra, and Desroches—each of which were excised from the then-Crown Colony of the Seychelles. The latter three sets of islands were never militarized and, as a result, were handed back to the Seychelles in 1976 upon that territory becoming an independent state. Because the United States only uses Diego Garcia for military purposes, Washington has little interest in keeping the outer Chagos Islands under UK control. These islands could therefore be returned to Mauritius immediately, pending a final agreement on the status of Diego Garcia. While it is unlikely that Mauritius will agree to give up its territorial claim to Diego Garcia altogether, Port Louis might agree upon an extended timetable for the transfer of sovereign control over that island—one that would provide certainty for all concerned, satisfy international demands for decolonization, and give the United States and Mauritius enough time to conclude a comprehensive bilateral agreement on the future use of Diego Garcia for military purposes.

In the long-term, though, the only option for the United States is to prepare for the eventual transfer of sovereignty over Diego Garcia as well as the outer islands. This cannot be avoided for several reasons. First, from the Mauritian perspective, Diego Garcia is just as much Mauritian territory as the other Chagos Islands. Port Louis will not give up its demands for total decolonization. However, as I have argued, there are also powerful reasons of self-interest for why the United States should prefer Mauritian sovereignty over Diego Garcia. Namely, it is possible that a future UK government will decide (or be forced) to decolonize without giving much notice to the United States—whether because of unbearable international pressure or because of a domestic change in attitudes toward the alliance with the United States. It would be better for the United States to cultivate a willing and enthusiastic partner in Port Louis rather than be left in the position of having to begin talks with Mauritius once decolonization has become a fait accompli.

In 2016, Mauritius assured the United Kingdom and United States that it had “no objection” to the continued use of Diego Garcia for military purposes.⁵⁰ This position has been the same since the early 1980s.⁵¹ Of course, this does not mean that discussions with Mauritius will be straightforward. There will have to be a bilateral status of forces agreement, for example, and an agreement over financial compensation—items that have never had to be negotiated with the United Kingdom because of the nature of the BIOT arrangement. Such talks might prove to be somewhat burdensome for the United States. Mauritius might wish to impose limits over the storage of certain weapons, for example (especially nuclear weapons),⁵² and could insist on Diego Garcia not being used for practices such as the detention of prisoners. However, there will be silver linings: concluding a formal agreement (treaty) with the government of Mauritius would give the US base on Diego Garcia a much firmer legal footing than it currently enjoys via the United Kingdom and the BIOT.

There is always a remote possibility that Mauritius will decide against hosting a US base on Diego Garcia, whether now or in the future. This is the case with every country that hosts a US military installation; foreign governments always have the outside option of denying the United States the right to conduct military operations on their sovereign territory. Nevertheless, the best outcome for the United States would be to convince decision makers in Port Louis that security cooperation with the United States is in their national self-interest. A self-enforcing voluntary agreement with Mauritius would be an infinitely more durable foundation for the base on Diego Garcia than continuing to rely upon the UK government’s ability to justify its occupation of an illegal colony before domestic and international audiences.

Convincing Mauritius of the benefits of close security cooperation with the United States should not be difficult. Mauritius does not have a standing army of its own, instead tacitly relying upon others to guarantee its national security and a tranquil regional environment. Moreover, there is already some military cooperation between the US and Mauritian governments—especially in terms of antipiracy operations. Hosting a US military base on Mauritian soil would allow Port Louis to upgrade its security ties with the United States to a level of a credible military partnership: cooperation over Naval Support Facility Diego Garcia would provide American leaders with an enduring stake in the military security and political independence of Mauritius—no small thing in the context of a shifting balance of power in the Indian Ocean region.

Once Mauritius assumes sovereignty over Chagos, it is likely that the archipelago will be treated as a discrete subnational jurisdiction. The model for this would be Rodrigues, which is an autonomous region of Mauritius and has its own regional assembly.⁵³ Talks should begin with Mauritius’s Ministry of Local Government and Outer Islands, then, to see whether there might be the potential for different laws and immigration rules to be put in place for Chagos than Mauritius proper, with a view to limiting tourism and the size of a permanent resettlement. If a new civilian administration in the Chagos Islands can borrow (as can Rodrigues) then this might even open the door to a direct financial relationship between the United States and a new autonomous government in Chagos in terms of lending, aid, and investment; the United States would have the chance to become a partner in facilitating the managed resettlement of Chagos rather than an impediment. It might even be the case that the unitary island of Diego Garcia could be organized into a discrete administrative unit, separate from both Mauritius proper and the outer Chagos Islands. If so, this would create additional opportunities for the base on Diego Garcia to be treated in a distinct fashion.

Talks should begin with the Chagossians, too. Mauritius has a checkered past when it comes to its treatment of the Chagossian diaspora, but, at least officially, Port Louis supports the resettlement of Chagos by the Chagossians (and, perhaps, other Mauritians).⁵⁴ US planners must therefore assume that Mauritian sovereignty over Chagos will be accompanied by the civilian resettlement of all or some of the islands. This would naturally pose some challenges for Naval Support Facility Diego Garcia. While not all islanders have protested the base in the past,⁵⁵ some have expressed their opposition to the US military. Others have formed political alliances with leftists in Mauritius who call for the shuttering of the base. For the most part, these have been “pragmatic” alliances.⁵⁶ Nonetheless, it means that the US government will face something of an uphill struggle to convince the islanders that their interests are compatible with those of the Pentagon.

There are several practical appeals that the United States could make to the islanders to ensure that resettlement need not compromise the security of the base on Diego Garcia. Indeed, it might even be the case that US leaders will have significant leverage in any conversations on resettlement. After all, the US military will have unique wherewithal to assist resettled civilians with everyday needs such as transport, communications, healthcare, and employment. If it undertakes to assist in the practicalities of resettlement, the Pentagon could secure for itself a meaningful say in the form and extent of any such efforts. If the United States continues to ignore the Chagossians, however—or if it engages with the islanders in a way that appears cynical, insincere, or insensitive—then this will only succeed in empowering those who wish to see the base closed.⁵⁷

Of course, it would be absurd to argue that the US base will be unaffected by the assumption of Mauritian sovereignty over (and resettlement of) the Chagos Islands. Without question, the base will have to change to accommodate new political realities. However, it is worth recapitulating what makes Diego Garcia so valuable to the US military in the first place: not just its political seclusion but its geographic endowments, too. And while the decolonization of the Chagos Archipelago will obviously undermine the political shelter that London has offered the US military since the BIOT’s creation in 1965, the geographic advantages offered by Diego Garcia are fixed. The goal of the United States should be to make sure that Diego Garcia can continue to be utilized to the maximum extent possible. In the current context, this means supporting Mauritian sovereignty instead of attempting to prop up the ailing colonial-era edifice that is the BIOT. The road to securing lasting access to Diego Garcia runs through Port Louis, not London.

A Crowded Ocean?

As a final note, it is worth remembering that it is not just US military strategists who have a stake in the future of Chagos. As Mauritian sovereignty over Chagos becomes more likely, other groups can be expected to fight for the ears of Mauritian politicians to shape the political situation in the islands. The exiled islanders are the most obvious constituency in this regard. And, as I have argued here, it is right and proper that the United States begin talks with the Chagossians to discuss ways to coexist in a post–BIOT political environment. However, the Chagossians are not the only group with an interest in Chagos. They might not even be the most powerful.

First, the international network of environmentalists who campaigned for the creation of an MPA in Chagos have a firmly vested interest in the future of the islands. After all, it was this group of campaigners who convinced the UK government to create an MPA in Chagos despite stark warnings from UK civil servants that such a move would create legal and political problems in terms of the BIOT’s long-term governance (as turned out to be the case). It is prudent to expect that this same coalition of environmentalists will remain engaged in Chagos during and after any transfer of sovereignty. The conservationists themselves have never been opposed to the base on Diego Garcia, preferring to work with the UK and US authorities to facilitate scientific research and conservation work. Indeed, those environmentalists most closely associated with Chagos have viewed the base through a positive lens—celebrating the unparalleled seclusion that its existence has brought upon the rest of the Chagos Archipelago.

That said, not all environmentalist groups are at ease with large military bases. Some take a dim view of Naval Support Facility Diego Garcia in particular. It is therefore possible that conservationist organizations might lobby Mauritian leaders to pursue a green legacy of their own in Chagos rather than continue to be associated with the US military. One obvious option would be for Mauritius to seek UNESCO World Heritage Site recognition for the Great Chagos Bank—the largest coral reef structure in the world, and one that has been left in near-pristine condition except for the waters around Diego Garcia.⁵⁸ Such a proposal might be eminently attractive to politicians in Mauritius because it would provide a public relations-friendly way to accommodate the Chagossians (as custodians of the natural environment),⁵⁹ attract revenue from ecotourism, and brandish Port Louis’s environmentalist credentials, while simultaneously bolstering Mauritius’s geopolitical status as a so-called large ocean state.⁶⁰

On a more strategic level, it is also possible that Mauritius could be approached by China or India (or both) when it comes to deciding the future of the Chagos Islands.⁶¹ Beijing has made significant efforts to court Indian Ocean states over the past decade, and New Delhi has a long history of involvement in Mauritian affairs—most recently concluding an agreement to establish coastal radar stations on Mauritian territory. Of the two, China would be most eager to see American forces evicted from Diego Garcia—but it is not a stretch to imagine that either of these Indo-Pacific powers would be interested in establishing naval bases of their own on Diego Garcia. Already, India has inked a deal with the Seychelles to establish a base on Assumption Island (the Seychelles). China, meanwhile, operates a military facility in Djibouti. Securing even limited access to Diego Garcia would be an enormous boon to either government. Guarding against the influence of America’s great power rivals over Mauritius will therefore be a high priority for US diplomats in a post-BIOT world. It can be done most easily by supporting Mauritian sovereignty as soon as possible and working to ensure that the US–Mauritian relationship is strong and self-enforcing.

Conclusions

In an article published in 1982, political scientist Joel Larus wrote that the US military presence on Diego Garcia might not be quite as durable as imagined by the architects of the 1966 executive agreement to establish the base.⁶² Larus called Diego Garcia a “crucial platform for the projection of U.S. military power throughout all sectors of the Indian Ocean, including the Persian Gulf-Arabian Sea”⁶³—an analysis that many scholars of international security would agree with today. However, he feared that the United Kingdom “appear[ed] to have acquired something less than full and unrestricted sovereignty in 1965” owing to Mauritius’s claims over the territory.⁶⁴ Moreover, he noted that domestic forces inside the United Kingdom—particularly on the left of the Labour Party—were hostile to US military interests and could not be regarded as reliable partners going forward. Both points seem prescient considering recent events.

Back then, Larus’s preferred solution was that the United States should seek sovereignty over Diego Garcia. This would no longer be feasible. Mauritius would never agree to it, and it would provoke uproar in the international community. Today, Mauritian sovereignty is the only way to resolve the political pathologies that undermine the security of Naval Support Facility Diego Garcia. The BIOT must be jettisoned altogether. Fortunately, the decolonization of Chagos is one of those rare occasions in US foreign policy where the realpolitik course of action also happens to be the moral and legally required thing to do. Even if it was not always thus, it is now: America’s long-term strategic interests would be best served by supporting the full decolonization of Chagos and working to make sure that Mauritian sovereignty over the islands will not jeopardize the longevity of the base on Diego Garcia. While there might be some costs associated with consigning the BIOT to history, the long-term benefits of cultivating a lasting strategic ally at the heart of the Indian Ocean are well worth it.

Dr. Peter Harris

Dr. Harris is an assistant professor of political science at Colorado State University, where his research and teaching focus on international security, US foreign policy, and international relations theory. He received his PhD in government from the University of Texas at Austin, where he was also a graduate fellow of the Clements Center for National Security, and holds additional degrees from the SOAS University of London and the University of Edinburgh. Dr. Harris is widely published in leading international relations journals, magazines, and blogs.

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