The Chagos Islands Explained: Why Diego Garcia Matters to the World
Indian Ocean Geopolitics: Islands, Sovereignty and Great Power Rivalry
The Island Chain That Shapes Global Strategy
Far from the world’s great capitals lies a remote chain of coral islands that few people can locate on a map. Yet these tiny islands have shaped global military strategy for over half a century and continue to influence the strategic calculations of the United States, Britain, India, China and other major powers. At the centre of this little-known archipelago lies Diego Garcia, arguably the most strategically important overseas military base in the Indian Ocean.
The Chagos Archipelago occupies a unique position near the geographical centre of the Indian Ocean, astride the sea lanes that connect the Persian Gulf, East Africa, South Asia and Southeast Asia. Every year, billions of dollars’ worth of energy supplies, manufactured goods and raw materials pass through these waters. Whoever maintains a strategic presence in this region enjoys a significant advantage in protecting trade, projecting military power and responding to crises across the Indo-Pacific.
Yet Chagos is more than a military asset. It is also the subject of one of the world’s longest-running sovereignty disputes, involving colonial history, international law, displaced island communities and the strategic interests of several global powers.
What Are the Chagos Islands?
The Chagos Archipelago consists of more than sixty small islands and coral atolls scattered across the central Indian Ocean. The largest and most important is Diego Garcia, a horseshoe-shaped atoll located about 1,800 kilometres south of India and roughly 2,200 kilometres north-east of Mauritius.
Although the islands occupy barely 60 square kilometres of land, they command an enormous maritime zone and sit close to some of the world’s busiest shipping routes. Their strategic value comes not from their size, but from their location.
Historically, Chagos formed part of Mauritius under both French and British colonial rule. For well over a century, the islands were administered together before events during the Cold War changed their destiny forever.
How Chagos Became a Global Dispute
As Britain prepared Mauritius for independence, it detached the Chagos Archipelago from the colony in 1965 and created the British Indian Ocean Territory (BIOT). Mauritius gained independence three years later, but without Chagos.
Mauritius has always maintained that the separation was unlawful because it occurred under colonial rule. Britain argued that the arrangement formed part of the independence negotiations. That disagreement remains the foundation of today’s sovereignty dispute.
The timing reflected Cold War realities. Britain and the United States wanted a secure military location in the Indian Ocean from which Western forces could monitor Soviet naval activity, protect vital shipping routes and support operations across the Middle East, Africa and Asia.
To make way for the military base, approximately 1,500 to 2,000 Chagossians were removed from their homeland between the late 1960s and early 1970s and relocated mainly to Mauritius and Seychelles. Their displacement remains one of the most controversial chapters in the archipelago’s history.
Why Diego Garcia Matters
Few military bases occupy a location as strategically valuable as Diego Garcia.
Situated near the centre of the Indian Ocean, the island allows military aircraft and naval forces to reach the Persian Gulf, East Africa, the Arabian Sea, South Asia and Southeast Asia without relying on multiple overseas bases. This central position has made it indispensable to American and British military planning for decades.
Construction of the base began in the early 1970s and it has since evolved into one of the United States’ most important overseas military facilities. Its long runway accommodates strategic bombers, while its deep-water harbour supports submarines, naval vessels and logistics ships. Massive fuel storage facilities and pre-positioned military equipment allow sustained operations far from the American mainland.
Diego Garcia played an important role during the 1991 Gulf War, military operations in Afghanistan following the September 11 attacks, and later campaigns in Iraq. Today, as strategic competition increasingly shifts towards the Indo-Pacific, the island has assumed even greater importance.
Military planners often describe Diego Garcia as an “unsinkable aircraft carrier”. Unlike naval task forces that must constantly move and replenish, the island provides a permanent logistics, intelligence and command hub from which operations can be sustained across much of the Indian Ocean.
Its significance extends beyond military operations. The base also supports maritime surveillance, humanitarian assistance, disaster relief and the protection of critical sea lanes through which much of the world’s trade and energy supplies pass.
The Long Road to Sovereignty
For Mauritius, the Chagos issue has always been about completing the process of decolonisation.
After decades of diplomatic efforts, the dispute increasingly shifted towards international legal institutions. A major breakthrough came in 2019 when the International Court of Justice concluded that Britain’s continued administration of the Chagos Archipelago was inconsistent with the process of decolonisation and advised that the United Kingdom should end its administration of the territory as rapidly as possible.
Although the opinion was advisory, it significantly strengthened Mauritius’ diplomatic position. The United Nations General Assembly subsequently adopted a resolution calling upon Britain to withdraw its administration from the islands.
Alongside the sovereignty dispute, the Chagossian community continued its own campaign for justice. Many former islanders sought recognition of their right to return, arguing that financial compensation could never replace the loss of their homeland, culture and identity.
A Community Still Seeking Justice
The Chagossian community is not entirely united on what the future should look like. While many continue to campaign for the right to return to their homeland, others have prioritised compensation, British citizenship and improved living conditions in Mauritius, Seychelles and the United Kingdom. Many recognise that Diego Garcia is unlikely to be opened for civilian settlement because of its strategic military role and instead advocate resettlement on the archipelago’s outer islands. These differing perspectives highlight the difficult balance between historical justice, national security and practical realities.
The Historic Agreement
Following years of negotiations, Britain and Mauritius reached a landmark agreement in 2025.
Under the arrangement, Britain agreed to recognise Mauritian sovereignty over the entire Chagos Archipelago, including Diego Garcia. At the same time, Mauritius agreed to lease Diego Garcia back to the United Kingdom for a period of 99 years, allowing the joint UK-US military base to continue operating without interruption.
The agreement also includes a long-term financial package, with Britain committing annual payments and economic support to Mauritius over the lease period, reflecting both the strategic importance of Diego Garcia and the wider political settlement.
The agreement sought to balance two competing realities. Mauritius achieved its long-standing objective of recovering sovereignty over Chagos, while Britain and the United States retained uninterrupted access to one of the world’s most strategically important military installations.
Not everyone welcomed the settlement. Critics, including US President Donald Trump, questioned whether transferring sovereignty over such a strategically valuable territory could create long-term security risks, particularly at a time when China is steadily expanding its influence across the Indian Ocean.
Supporters, however, argued that the agreement resolved one of the last major colonial disputes while preserving the military base that underpins regional security.
Where Does the Agreement Stand Today?
Although Britain and Mauritius signed the landmark agreement in 2025, its implementation has not been entirely straightforward. Political debate in both countries, questions over ratification, concerns expressed by US President Donald Trump about the long-term strategic implications, and differing views within the Chagossian community have all influenced subsequent discussions. While the agreement preserves the continued operation of the UK-US military base on Diego Garcia, negotiations over resettlement, compensation and future governance of the outer islands continue to evolve.
India’s Carefully Balanced Position
India has consistently supported Mauritius’ sovereignty over the Chagos Archipelago, reflecting New Delhi’s long-standing commitment to decolonisation and international law.
At the same time, India also recognises the strategic importance of Diego Garcia in maintaining stability across the Indian Ocean. As China’s maritime presence expands through ports, infrastructure projects and naval deployments, the continued operation of the UK-US military facility contributes to the broader balance of power in the region.
Rather than viewing these positions as contradictory, India has adopted a pragmatic approach by supporting Mauritian sovereignty while acknowledging the security realities that make Diego Garcia indispensable to regional stability.
Why China Is Watching Closely
Although China is not directly involved in the Chagos dispute, developments are followed carefully in Beijing. Diego Garcia occupies a commanding position near the maritime routes connecting the Persian Gulf with the wider Indo-Pacific, through which a significant share of China’s energy imports and international trade pass. As China expands its naval presence and commercial investments and maritime infrastructure projects across the Indian Ocean, the continued operation of the UK-US military facility remains an important element of the region’s strategic balance. The future of Chagos therefore carries implications well beyond Britain and Mauritius.
Other Island Disputes in the Indian Ocean
The Chagos Archipelago is not the only island dispute in the Indian Ocean, although it is by far the most strategically significant.
France continues to administer Mayotte, despite sovereignty claims by the Comoros. Tromelin Island remains disputed between France and Mauritius, while Katchatheevu periodically features in political debate between India and Sri Lanka, particularly over fishing rights.
These disputes underline an enduring geopolitical reality: small islands often carry strategic importance far greater than their physical size.
Beyond sovereignty, many Indian Ocean islands also face growing environmental challenges. Low-lying coral atolls are particularly vulnerable to rising sea levels, coastal erosion and climate change. Environmental concerns have also featured in the Chagos debate, including controversy surrounding the Marine Protected Area established by Britain in 2010, which Mauritius argued affected its sovereign rights and the future livelihoods of displaced islanders.
Key Timeline
- 1814: Britain assumes control of Mauritius and the Chagos Archipelago.
- 1965: Chagos is separated from Mauritius to create the British Indian Ocean Territory (BIOT).
- 1968: Mauritius gains independence.
- 1971: Construction begins on the joint UK-US military base at Diego Garcia.
- 2019: International Court of Justice advises that Britain should end its administration of Chagos.
- 2025: Britain and Mauritius sign a landmark sovereignty agreement.
- 2026: Ratification, implementation and resettlement discussions continue while Diego Garcia remains fully operational under the lease arrangement.
A Small Archipelago with Global Consequences
The Chagos Archipelago demonstrates that geography continues to shape international politics. Barely visible on most world maps, these remote coral islands have influenced Cold War strategy, international law, military planning and great-power competition for more than half a century.
For Mauritius, Chagos represents the completion of decolonisation. For the Chagossian people, it remains a deeply personal struggle for justice and identity. For Britain and the United States, Diego Garcia continues to be an indispensable military asset. For India, it reflects the careful balance between supporting international law and preserving regional security. For China, it forms part of the wider strategic landscape of the Indo-Pacific.
As global attention increasingly shifts towards the Indian Ocean, the importance of the Chagos Islands is unlikely to diminish. History has repeatedly shown that control of the seas often depends upon a handful of strategically located islands. Few places illustrate that timeless lesson more clearly than the Chagos Archipelago and Diego Garcia.
Also Read Related TNT Articles:
The Battle for the Indian Ocean – Part I: The Ocean That Powers the World
The Battle for the Indian Ocean – Part II (TBA)
