Knowledge Nugget | UK hands over Chagos Islands to Mauritius: All you need to know for UPSC Exam

Why in the news?

UK Prime Minister Keir Starmer Thursday (May 22) signed a deal transferring sovereignty of the Chagos Islands to Mauritius, including the key Diego Garcia military base. The base, which plays a central role in UK-US defence operations in the Indian Ocean, will now be leased from Mauritius under a new 99-year lease.

Key Takeaways :

1. Under the deal, the UK will pay Mauritius an average of £101 million ($129m) per year — amounting to a total of £3.4 billion ($4.35 billion) over the course of the lease. Starmer also claimed the arrangement would cost less than operating an aircraft carrier annually.

2. The US, which co-operates the Diego Garcia base with the UK, will shoulder the base’s operational costs — which Starmer said exceed the UK’s financial contribution. US President Donald Trump voiced his support for the deal in February following a meeting with Starmer in Washington.

Chagos Archipelago

1. The Chagos archipelago comprises more than 60 low-lying islands in the Indian Ocean roughly 1,600 km to the northeast of the main island of Mauritius. Chagos has a land area of only 56.1 sq km, with Diego Garcia alone spread over 32.5 sq km — which is about the same as the land area of Lakshadweep.

2. Including the lagoons within its atolls, however, Chagos has a total area of more than 15,000 sq km. The Great Chagos Bank, spread over 12,642 sq km, is the world’s largest atoll structure.

3. The Chagos islands remained uninhabited until the late 18th century, when the French brought in enslaved laborers from Africa and India to work on newly established coconut plantations. In 1814, under the Treaty of Paris, France ceded Mauritius—including the Chagos Archipelago—to the British.

Map showing Chagos Islands.

4. In 1965, the UK constituted the British Indian Ocean Territory (BIOT), of which the Chagos Islands were a central part. The BIOT was meant to provide the British (and by extension their Cold War allies, the Americans) with an overseas base in the Indian Ocean.

5. Chagos was attached to Mauritius, another British colony in the Indian Ocean, for administrative purposes. But when Mauritius gained independence in 1968, Chagos remained with Britain. The UK government gave the newly-independent country a grant of 3 million pounds over the “detachment” of the Chagos archipelago.

BEYOND THE NUGGET: Diego Garcia

1. Diego Garcia is the largest island in the Chagos Archipelago, located in the Indian Ocean. In 1966, Britain signed an agreement with the US which made the BIOT available for the two countries’ defence needs. Land was acquired in 1967, and four years later, the plantation on Diego Garcia was shut down.

2. Diego Garcia became a fully operational military base in 1986. It has played a pivotal role in military operations, including US-UK strikes on Houthi targets in Yemen (2024–2025), humanitarian missions to Gaza, and earlier, bombing campaigns against the Taliban and al-Qaeda in Afghanistan in 2001.

3. “Diego Garcia is the site of a joint U.S.-UK military facility that plays a vital role in national, regional, and global security. It enables the United States to support operations that demonstrate our shared commitment to regional stability, provide rapid response to crises, and counter some of the most challenging security threats we face.” – Former U.S. President Joe Biden said this in October 2024.

4. Notably, Diego Garcia is a coral atoll and southernmost member of the Chagos Archipelago. It is located 7 degrees south of the equator.

Post Read Questions

(1) With reference to the Chagos archipelago, consider the following statements:

1. It lies to the south of the Maldives archipelago in the Indian Ocean.

2. These islands were uninhabited until the late 18th century.

3. In 1814, France ceded the islands to the Portuguese.

Which of the statements given above are correct?

(a) 1 and 2 only

(b) 2 and 3 only

(c) 1 and 3 only

(d) 1, 2 and 3

(2) Diego Garcia, the largest island of the Chagos Archipelago is located in:

(a) Central Indian Ocean

(b) Southern Indian Ocean

(c) Southern Arabian Sea

(d) Southern Bay of Bengal

(Sources: UK-Mauritius treaty on Chagos Archipelago, Diego Garcia, UK hands over Chagos Islands to Mauritius for £101 million a year in last-minute deal)

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