Britain’s 1965 acquisition of the remote Indian Ocean archipelago has been disputed ever since. In 2019, the United Nations ruled that the UK should hand back the roughly 55 islands and atolls.

After British Prime Minister Keir Starmer on Thursday signed a deal — following legal wrangling — to return the islands to Mauritius, here are some key details about Chagos:

Indian Ocean Colony

Located several hundred kilometres (miles) south of the Maldives, the Chagos Islands were colonised by France in the 18th century, and African slaves were shipped in to cultivate coconuts and copra.

In 1814, France was made to cede the islands to Britain, which in 1903 merged them with Mauritius, its colony around 2,000 kilometres (1,200 miles) to the southwest.

After the abolition of slavery in 1834, Indian workers arrived and mixed with the first settlers. Only three of the islands were inhabited: Diego Garcia, Salomon, and Peros Banhos.

Mass Eviction

In 1965, Britain separated the Chagos Islands from the rest of Mauritius, then a semi-autonomous British territory eyeing independence.

Britain paid three million pounds for them, the equivalent of around 50 million pounds ($65 million) today.

When Mauritius became independent three years later, the islands remained under British control and were renamed the British Indian Ocean Territory (BIOT).

In 1966, Britain leased the islands to the United States for 50 years to set up a military base. In 2016, the deal was extended to 2036.

Between 1968 and 1973, around 2,000 Chagos islanders were evicted, a move described in a British diplomatic cable at the time as the removal of a “few Tarzans and Man Fridays.”

Most were shipped to Mauritius and the Seychelles.

Mauritius argued it was illegal for Britain to break up its territory and demanded the right to resettle former residents.

Strategic Military Base

The US military base on Diego Garcia, the largest island, became of major strategic importance during the Cold War.

It offered proximity to Asia as an assertive Soviet navy extended communist influence in the Indian Ocean.

After the 1979 Iranian revolution, the United States expanded the base to receive more warships and heavy bombers.

In recent years, it served as a staging ground for US bombing campaigns in Afghanistan and Iraq.

Islanders Take Action

Chagos islanders living in Mauritius launched legal proceedings in 1975 against their expulsion, resulting in a 1982 payment of four million pounds in compensation, along with land valued at one million pounds.

There were no reparations for islanders settled in the Seychelles.

In 2007, a British appeals court allowed Chagossians to return home, but the upper House of Lords annulled its decision the following year.

In 2016, the British government confirmed its opposition to the resettlement of Chagossians, including for reasons of defence, security, and cost.

Around 10,000 Chagossians and their descendants are divided between Mauritius, the Seychelles, and Britain.

ICJ Ruling

In 2010, Britain declared the islands part of a Marine Protected Area, arguing that people should not be permitted to live there.

Diplomatic cables revealed by WikiLeaks quoted a British official as saying the plan “put paid to the resettlement claims of the archipelago’s former residents”.

The move backfired, as a UN arbitration tribunal declared it illegal in 2015. In 2019, the International Court of Justice (ICJ) stated that Britain had illegally split the islands and should relinquish control.

Britain rejected the ruling, insisting that Mauritius was wrong to bring the case to court, and arguing the Diego Garcia base played a “vital role” in keeping the region safe.

Later that year, a UN General Assembly resolution demanded Britain cede the islands.