UK Transfers Chagos Islands to Mauritius Amidst Geopolitical Tensions and Iran Missile Strike on Diego Garcia

The United Kingdom's agreement to transfer sovereignty of the Chagos Islands to Mauritius, while securing a long-term lease on the strategic Diego Garcia military base, has generated significant international discussion. This development coincides with escalating tensions in the Middle East, marked by an Iranian drone strike on a British base in Cyprus and subsequent missile launches targeting the Diego Garcia facility. These events have led to a shift in the UK's policy on allowing U.S. forces to use its bases for defensive operations against Iran.

Former U.S. President Donald Trump has publicly expressed strong criticism of the Chagos deal, linking it to broader U.S. national security interests and his previous advocacy for acquiring Greenland.

Chagos Islands Sovereignty Agreement

The United Kingdom and Mauritius reached an agreement in 2024 for the UK to transfer sovereignty over the Chagos Islands to Mauritius. This decision addresses a long-standing dispute and follows a 2019 non-binding advisory opinion by the International Court of Justice (ICJ) and subsequent support from the UN General Assembly. The UN recommended the UK relinquish control and complete the decolonization of Mauritian territory "as rapidly as possible."

The transfer of sovereignty over the Chagos Islands is scheduled for May 2025.

Under the terms of the agreement, the UK will retain control of the joint UK-U.S. military base on Diego Garcia, the largest island in the archipelago, through a 99-year lease with an option for a 50-year extension. The UK government will pay Mauritius an average annual sum of £101 million ($135.7 million), with the net cost of the lease estimated at £3.4 billion. Public estimates suggest the total cost to British taxpayers, including compensation, could reach approximately £35 billion ($47 billion) over the next century. The agreement also includes a 24-mile buffer zone around Diego Garcia where construction would require UK consent.

Historical Context and Rationale

Historically, the Chagos Islands were separated from Mauritius in 1965, three years before Mauritian independence, to establish the British Indian Ocean Territory (BIOT). Between 1967 and the early 1970s, the indigenous Chagossian population was forcibly removed from the islands, primarily to Mauritius and Seychelles, to facilitate the construction of the military base. Mauritius has consistently maintained its sovereignty claims over the archipelago.

The UK government's stated rationale for the deal is to safeguard the operations of the joint UK-U.S. military base on Diego Garcia for future generations. They cite that previous court decisions had undermined the UK's position and threatened the base's operational capabilities. Mauritius's Attorney General, Gavin Glover, has emphasized that the deal was negotiated bilaterally, and international law unambiguously recognizes Mauritius's sovereignty.

Strategic Importance of Diego Garcia

Diego Garcia serves as a strategically vital U.S. military base, acting as a cornerstone of American defense infrastructure in the Indian Ocean. It supports operations in the Middle East, Indo-Pacific, and Africa, accommodating long-range bombers and housing approximately 2,500 military and civilian personnel.

Former President Trump's Intervention

Former U.S. President Donald Trump has publicly criticized the Chagos Islands sovereignty transfer, describing it as "an act of great stupidity" and "total weakness." He asserted that the transfer was "FOR NO REASON WHATSOEVER" and claimed that nations like China and Russia would interpret such an action as a sign of weakness.

Linking Chagos to Greenland Interests

Trump further linked the Chagos situation to his previously expressed interest in the United States acquiring Greenland, stating that it is "imperative for National and World Security." He also suggested that British Prime Minister Keir Starmer was "losing control of this important Island by claims of entities never known of before," characterizing these claims as "fictitious in nature."

These recent statements by Trump represent a shift from his administration's earlier stance. In May of the previous year, then-Secretary of State Marco Rubio affirmed that a comprehensive interagency review had determined the agreement "secures the long-term, stable, and effective operation of the joint U.S.-UK military facility at Diego Garcia," and that Trump had expressed support for this "monumental achievement."

Revealed Text Exchanges on Greenland

In January 2026, text exchanges between former President Trump and European leaders regarding Greenland were released. In messages, Norwegian Prime Minister Jonas Støre contacted Trump concerning Greenland, Gaza, Ukraine, and tariffs. Trump responded by questioning Denmark's right to Greenland and advocating for "Complete and Total Control of Greenland" for global security, linking it to his contributions to NATO. French President Emmanuel Macron messaged Trump, expressing alignment on Syria and potential collaboration on Iran, but stated he "did not understand" Trump's position on Greenland. NATO Secretary General Mark Rutte also messaged Trump, commending his actions in Syria and committing to finding a resolution regarding Greenland.

Warning of Military Force

Amidst his criticism, Trump also warned that if the Diego Garcia lease agreement were to fail or if U.S. operations were threatened, the United States could use military force to secure and reinforce its presence on the base. Downing Street confirmed that Starmer and Trump recently discussed Diego Garcia and agreed on the importance of safeguarding the base’s continued operation.

UK Parliamentary Debate and Conservative Opposition

The Chagos Islands deal has faced opposition within the UK. A House of Lords debate on the legislation to ratify the agreement was postponed after the Conservative Party tabled an amendment calling for a pause due to "changing geopolitical circumstances."

Conservatives argued that passing the bill could contravene a 1966 Treaty with the United States, which stipulates that the territory "shall remain under UK sovereignty," potentially breaching international law.

They requested ministerial agreement with the U.S. regarding the 1966 Treaty before the bill's reintroduction to the House of Lords. The UK government spokesperson attributed the delay to ongoing discussions with the U.S. and affirmed commitment to the deal for national security.

Escalating Tensions with Iran and Military Base Access

Geopolitical tensions involving Iran have intertwined with the Chagos Islands discussions. In late February 2026, British Prime Minister Keir Starmer reportedly denied an initial U.S. request to use UK air bases, including RAF Fairford in England and Diego Garcia, for a preemptive attack on Iran, citing concerns about compliance with international law.

Policy Shift After Cyprus Strike

However, this stance evolved following a drone strike on the British military base RAF Akrotiri in Cyprus in early March. Subsequently, the UK government agreed to a U.S. request for permission to use British bases for specific and limited defensive operations aimed at preventing Iran from firing missiles across the region, protecting partner countries, and British citizens. This authorization included targeting Iranian missile sites, particularly those involved in attacks on shipping in the Strait of Hormuz.

Prime Minister Starmer justified this policy shift as necessary to prevent further escalation and protect lives, while clarifying that RAF Akrotiri would not be used for offensive operations against Iranian missile sites. Foreign Secretary Yvette Cooper stated the UK would not engage in offensive action and held "a different view from the US and Israel" on the conflict.

Missile Incident Targets Diego Garcia

On March 20, 2026, Iran reportedly launched two intermediate-range ballistic missiles towards the joint U.S.-UK military base on Diego Garcia. According to U.S. and Israeli officials, one missile was intercepted by a U.S. warship, while the other reportedly failed mid-flight or fell short.

Neither missile came close to the base.

Iran, through its Foreign Ministry spokesman Esmaeil Baghaei, denied responsibility for the launches, describing the claim as an an "Israeli false flag" attack and "disinformation."

Iran's Missile Capabilities

Diego Garcia is approximately 3,800 to 4,000 kilometers (2,360 to 2,500 miles) from Iran. This distance exceeds Iran's previously declared 2,000-kilometer self-imposed range limit for its ballistic missiles. Analysts have speculated that Iran may have modified existing missiles, such as the Khorramshahr, to extend their range by reducing payload, or potentially used a Simorgh space launch vehicle as an improvised missile.

International Responses

The incident prompted varied international responses:

• UK government: Condemned what it called "reckless Iranian attacks" and urged Iran to de-escalate. Defence Secretary John Healey confirmed the launches, stating neither missile came close to Diego Garcia.
• Israel Defense Forces (IDF): Claimed Iran possesses 4,000 km range weapons, suggesting they could pose a threat to European cities, including Berlin, Paris, Rome, and London. Israel's military chief, Eyal Zamir, specifically alleged the use of a "two-stage intercontinental ballistic missile."
• UK Communities Secretary Steve Reed: Stated there was no UK assessment supporting the claim that Iran intended to attack Europe or possessed the capability to do so.
• Analysts: Suggested the attempted attack on Diego Garcia, regardless of its success, challenges prior assumptions about Iran's missile capabilities and could indicate a geographical expansion of the conflict, potentially increasing global risks.

Prime Minister Starmer has scheduled a Cobra meeting to discuss the cost-of-living implications of the ongoing conflict. The UK, along with 21 other nations, issued a joint statement condemning Iran's attacks on commercial vessels and oil/gas facilities in the Middle East.