Diego Garcia in the Chagos Archipelago as a US–UK strategic foothold in the Indian Ocean

The Chagos Archipelago is a group of islands in the Indian Ocean, roughly 500 kilometres south of the Maldives and halfway between Africa and Indonesia. In 1814 France ceded the archipelago to Britain under the Treaty of Paris, and it was made part of the British colony of Mauritius.

In 1965 Britain, in breach of UN Declaration No. 1514 on the granting of independence to colonial countries and peoples — which guarantees the territorial integrity of colonies and their right to independence — passed the British Indian Ocean Territory law, under which the Chagos Archipelago was detached from Mauritius and kept under British control. Mauritius gained independence on 12 March 1968.

Yet on the basis of a UN General Assembly resolution adopted in June 2017 (with the United States and Britain opposed), the International Court of Justice ruled in February 2019 that Britain must hand control of the Chagos Islands in the Indian Ocean to Mauritius and “complete the decolonisation of the territory, taking account of the right of its inhabitants to self-determination”, thereby finding that the islands’ detachment in 1965 and their inclusion in the British Indian Ocean Territory were unlawful.

On 22 May 2019 the UN General Assembly adopted a resolution supporting the ICJ ruling by a large majority (116 votes in favour, 6 against and 56 abstentions). Britain refused to comply. All the same, on 3 October 2024 Britain agreed with Mauritius to transfer sovereignty over the Chagos Archipelago, including Diego Garcia, where a British–American military base is located. The base will remain under British control for 99 years to ensure it can keep operating without interruption. Diego Garcia hosts a British Navy support facility leased to the United States Navy.

Diego Garcia is of strategic value to the United States and Britain because it allows them to control international maritime traffic between the fast-growing regions of South-East Asia, South Asia, the Middle East and Africa. Control of the island also gives them leverage over the countries of those regions at the geopolitical and geo-economic level. The air base on Diego Garcia, for example, was used by American aircraft in the bombing of Afghanistan and Iraq. The CIA used the base to hold and interrogate terrorism suspects. In 2016 the American lease was extended to 2036. The island will matter greatly in a future US–China contest over South-East Asia, since it would allow China’s maritime trade routes across the Indian Ocean to be blocked.