Diego Garcia: The Shifting Sands of Sovereignty and Security

The future of Diego Garcia, a strategically vital island in the Indian Ocean, is once again the subject of intense debate. A 2025 agreement between the UK and Mauritius to transfer sovereignty of the Chagos Archipelago, of which Diego Garcia is a part, has sparked controversy, drawing criticism from the United States and raising questions about the long-term security of the base. This article examines the complex geopolitical factors at play, the details of the agreement, and the potential implications for the US, UK, and Mauritius.

A Colonial Legacy and Strategic Importance

The Chagos Islands, including Diego Garcia, have been under British control since 1814. The archipelago’s significance grew dramatically during the Cold War, with Diego Garcia becoming a crucial military base for the US. It has supported US military operations spanning from the Vietnam War to conflicts in Iraq and Afghanistan. Today, the base remains a critical hub for operations in the West Asia, East Africa, and the Indo-Pacific regions.

The 2025 Agreement: Sovereignty Transfer and Long-Term Lease

In May 2025, the UK and Mauritius reached an agreement to transfer sovereignty of the Chagos Archipelago to Mauritius. Under the terms of the treaty, the UK will retain operational control of Diego Garcia through a 99-year lease, with the option to extend. This arrangement aims to balance Mauritius’ claim to sovereignty with the continued strategic needs of the UK and the US.

US Concerns and Trump’s Intervention

The agreement has faced opposition from some quarters, most notably from former US President Donald Trump. Trump publicly cautioned the UK against proceeding with the transfer, arguing that it could jeopardize the base’s future, particularly in the context of potential conflicts involving Iran. He expressed concerns about the implications of a long-term lease, stating that leases are not a reliable arrangement when it comes to countries. His comments caused a pause in the parliamentary process in the UK for ratification, though the State Department continued to endorse the agreement.

Negotiations with Mauritius and Security Arrangements

Despite Trump’s objections, the US announced in February 2026 that it would launch formal negotiations with Mauritius to maintain its military footprint on the Chagos Archipelago. A three-day summit convened in Port Louis, Mauritius, beginning February 23, 2026, to focus on establishing “effective implementation of security arrangements” for the base. The US is similarly maintaining parallel discussions with London.

Safeguards and Restrictions within the Agreement

The agreement includes provisions designed to address security concerns. It allows the UK and US unrestricted rights to patrol the Chagos Archipelago and gives the UK a veto over spy ships, foreign bases, and even civilian development. The presence of foreign security forces requires authorization from both the UK and Mauritius. Mauritius has also agreed not to authorize the placement of maritime installations or artificial islands without UK consent.

Nuclear Weapons and Inspections

The agreement addresses the issue of nuclear weapons. While Mauritius has a treaty prohibiting the stationing of nuclear weapons on its territory, the UK’s lease allows for the temporary presence of nuclear weapons on Diego Garcia. The agreement also explicitly excludes any obligation for the UK to comply with treaties to which it is not a party, such as the Treaty of Pelindaba, thereby avoiding compulsory inspections.

Looking Ahead

The situation surrounding Diego Garcia remains fluid. The ongoing negotiations between the US and Mauritius, coupled with the UK’s commitment to the agreement, suggest a path forward that seeks to balance sovereignty claims with strategic security interests. The ultimate guarantor of the base’s security remains US military power, but the agreement offers a degree of legitimacy that has been lacking in the past. The coming months will be crucial in determining whether a stable and mutually acceptable arrangement can be established, ensuring the continued operation of this vital strategic asset.