In the 19th century, Britain took control of the Chagos Archipelago, a group of 60 small islands in the Indian Ocean that were originally part of Mauritius, a British colony. But when Mauritius gained its independence in 1968, the Chagos Islands were not returned. Instead, Britain kept control of the islands, separating them from Mauritius. The largest of these islands, Diego Garcia, became home to a US-British military base.

For decades, Mauritius and its people have fought to get the C...