- UK deal to transfer sovereignty of Chagos Islands to Mauritius has raised ‘uncertainties about whether or not the US can continue its operations,’ says Nitya Labh of Chatham House

 - ‘Near-term strikes on Iran will not hinge on the longer-term questions of sovereignty and basing ... but the possibility of a sustained campaign in the region places a premium’ on Diego Garcia, says Isaac Kardon of Carnegie Endowment for International Peace

WASHINGTON

Sitting in the middle of the Indian Ocean is a tropical island whose pristine white beaches and azure waters bely a highly strategic military base that has become a source of tension between Washington and London.

The joint US-UK base on the island of Diego Garcia, part of the Chagos Islands, has drawn renewed attention as conflict between the US, Israel and Iran escalates, and Washington weighs how to sustain military operations across the Middle East.

The remote installation has long been a cornerstone of US military planning, but its strategic importance has come into sharper focus in recent weeks.

“The UK has been very, very uncooperative with that stupid island that they have,” US President Donald Trump told reporters Tuesday in the Oval Office, referring to Britain’s reluctance to allow US forces to use the Diego Garcia base during the initial strikes on Iran.

He added that the UK’s decision to block the US from using the base on Saturday forced the US to spend “three or four days to work out where we can land.”

Starmer defended the decision, telling lawmakers that the UK did not support “regime change from the skies,” but added that Britain is now allowing its bases to be used for “defensive operations” to protect British citizens and allied forces in the region.

Transfer of sovereignty

The site previously rose to public attention in the US after Trump roundly criticized an agreement for the UK to transfer sovereignty of the Chagos Islands to Mauritius, while securing a 99-year lease for London to continue operating the joint base.

“Trump’s most consistent habit is to be totally inconsistent about important issues. His impulses about Diego Garcia vacillate, but he is likely acting on advice that ‘D-Gar’ is an irreplaceable asset for American power,” Isaac Kardon, the senior fellow for China studies at the Carnegie Endowment for International Peace think tank, told Anadolu.

“US defense posture hinges on continued access, basing and overflight in the former British territory. It is the essential platform for US joint forces to project combat power across the entire Indo-Pacific theater,” he added.

In mid-February, Trump said on his Truth Social platform that the US may need to use the base “to eradicate a potential attack by a highly unstable and dangerous regime.”

“Starmer is losing control of this important island by claims of entities never known of before,” he added.

The presidential broadside was made in the midst of a massive redeployment of American forces to the Middle East from Latin America. Kardon said the major shift in military power “likely requires substantial use of the Diego Garcia facilities."

“Near-term strikes on Iran will not hinge on the longer-term questions of sovereignty and basing in the remote island,” Kardon added. “But the possibility of a sustained campaign in the region places a premium on this unique asset.”

Secretive base central to US wars

Britain took control of Chagos and Mauritius in 1814 under the Treaty of Paris, then separated them in 1965 to create the British Indian Ocean Territory before Mauritius gained independence in 1968. Britain said the islands would be returned to Mauritius when no longer needed for defense.

Mauritius has claimed sovereignty since the 1980s and taken the case to international courts. In 2019, the International Court of Justice said Mauritius’s decolonization had not been lawfully completed and that Britain was “under an obligation to bring to an end its administration of the archipelago as rapidly as possible.”

Entry to the highly secretive Diego Garcia base is rarely granted to people outside the military or vetted contractors working at the site. That cohort of individuals accounts for the island’s entire population after its native inhabitants were forcibly transferred by the British in the 1960s and 1970s so the facility could be built and later secured.

The BBC gained rare access to the base in 2024 to cover an immigration case that was being adjudicated there – one of a handful of known exceptions to the base’s stringent access restrictions.

The tight lid kept on the site has helped it remain out of the public spotlight, but military observers point out that it has been instrumental in launching successive US military campaigns over the past decades.

Nitya Labh, the Schwartzman Academy fellow at Chatham House’s International Security Program, told Anadolu that the base was used as a “critical, high-volume launchpad for US air operations” in the 1991 Gulf War, as well as the subsequent 2003 US invasion of Iraq.

It was further used to launch strikes on Yemen’s Houthi rebels under the Biden administration in 2024 and the Trump administration in 2025.

“Since the establishment of the base in Diego Garcia, the US has often used it to support important military operations,” Labh said, noting that it is the sole US military base in the Indian Ocean.

UK-Mauritius deal clouds base’s future

The base’s long-term future has become more complicated following the sovereignty deal between Mauritius and the UK.

Labh said the deal has raised “uncertainties about whether or not the US can continue its operations in the Chagos Archipelago unhindered by any additional conditions or requirements.”

“Ultimately, the final terms and conditions will have to be resolved between Mauritius, the UK and the US,” she said. “Ideally, it would also take into consideration the rights and voices of the Chagossians.”

The debate over the site’s future remains contentious in the UK, where legislation to codify the agreement in law is still under consideration in Parliament.

The government has insisted that the deal it struck with Mauritius remains in place, after Foreign Office Minister Hamish Falconer said London was putting it on pause while talks with Washington continued.

“There is no pause, we have never set a deadline and timings will be announced in the usual way,” an anonymous government source told the BBC last week.