On October 3, the United Kingdom and Mauritius announced that they had reached an agreement on the retrocession of the Chagos Archipelago to Mauritius. While some have described the consequences of this deal as a “win-win” situation, others suggest it as a case of British strategic ineptitude. Meanwhile, this historic agreement was closely monitored in France, the last European sovereign nation in the region.
The French presence in the Indian Ocean region began in the 17th century and extended as its peak over many southwestern insular regions of the Indian Ocean (Madagascar, Mauritius, Comoros, Seychelles) as well as the trading posts of the Indies (Surat, Pondicherry, Chandernagore, Mahé, Yanaon, Karikal). Nowadays, France remains sovereign in several territories in the Indian Ocean region, including La Réunion Island, Mayotte, the subantarctic islands and the “Scattered Islands” (five uninhabited coral islands around Madagascar, including Tromelin).
These territories comprise nearly 2.6 million square kilometers – or 25 percent – of France’s Exclusive Economic Zone (EEZ), the second largest worldwide after the United States. This sizable foothold in the Indian Ocean contributes to France’s ambition to become a credible regional power in the Indo-Pacific Region.
However, French sovereignty over some of these territories is contested. Mayotte is claimed by Comoros, while three of the Scattered Islands (Glorieuses, Juan de Nova, and Bassas da India) are contested by Madagascar, and the island of Tromelin by Mauritius.
Map by Paco Milhiet.
History of Tromelin Island: Abandoned Castaways and Translation Disputes
Located over 400 km east of Madagascar and 550 km north of La Réunion, Tromelin Island is an uninhabited coral atoll, home only to rotating gendarmes and scientific personnel. Remote from major trade routes, the island is mostly known for its tragic history. Following a shipwreck in 1761, 80 Malagasy slaves were abandoned on the island for 15 years (1761-1776). When Commander Tromelin, who gave his name to the island, finally arrived to rescue them, only seven women and one child had survived.
Tromelin Island has been claimed by Mauritius since 1976. The Mauritian government contends that the island should have remained under British sovereignty following the Treaty of Paris in 1814. French and Mauritian diplomats continue to debate the translation of Article 8 of the treaty. The French text specifies that “the island of France [the former name of Mauritius] and its dependencies, namely Rodrigues and the Seychelles,” were to be ceded to Britain – an interpretation French diplomacy considers exhaustive.
Mauritians refer to the English version, which uses the adverb “especially” in reference to Rodrigues and the Seychelles, suggesting the list was not meant to be exhaustive. Mauritian diplomacy further argues that other islands not explicitly mentioned in the treaty, such as Saint-Brandon and Agalega, are now under Mauritian sovereignty. Additionally, British authorities issued concessions for guano exploitation on Tromelin between 1901 and 1951.
Every year, the two nations debate this issue before the Indian Ocean Tuna Commission.
In an effort to ease tensions, France and Mauritius, both partners in the Indian Ocean Commission, signed an economic, scientific, and environmental co-management agreement for Tromelin on June 7, 2010. However, the French Parliament has never ratified the agreement, perpetuating the competing claims between the two countries over the atoll.
Tromelin and Chagos Analogies
The recent Mauritius-U.K. agreement regarding the Chagos Islands will likely encourage Port Louis to pursue its sovereignty claims over Tromelin. That said, there are significant differences between the two situations. Unlike the Chagos, Tromelin does not host a major U.S. military base, and no civilian population was deported. However, the Mauritian authorities often associate the two territories to reinforce their historical claim, as highlighted in President Prithviraj Roopun’s speech at the U.N. General Assembly in September 2024.
In recent years, Mauritian diplomacy has developed a powerful repertoire of international actions to assert its sovereignty over the Chagos Islands, ranging from explicit support from several countries (notably China, India, and Russia) to favorable decisions from international instances, such as the advisory opinion from the International Court of Justice, The International Tribunal for the Law of the Sea, resolutions from the U.N. General Assembly, and support from the African Union.
Once the deal concerning the Chagos is finalized through a treaty with the United Kingdom, it is likely that Mauritian diplomatic efforts will shift focus toward the island of Tromelin. This presents a dilemma for French diplomacy, which is already familiar with similar situations involving its other territories in the Scattered Islands. The Republic of Madagascar has contested French sovereignty over these islands since 1973, supported by the U.N. General Assembly, the African Union, and Russia.
Consequences for France’s Wider Indo-Pacific Strategy
The French government has rejected all restitution claims and President Emmanuel Macron asserted French sovereignty over these territories in 2019, becoming the first president to visit the Scattered Islands. Other regional territorial disputes are undermining France’s strategy in the broader Indo-Pacific region, including Comoros’ claims regarding Mayotte and a tense decolonization situation in New Caledonia.
Often accused of harboring colonial ambitions by its neighbors in the Indian and Pacific Oceans, French diplomacy faces a dilemma: Should the state uphold the founding principles of unity, inalienability, and indivisibility of the Republic, thereby defending French sovereignty over these territories uncompromisingly against any foreign intrusion and without sharing? Or should France, on the contrary, develop innovative solutions in partnership with neighboring states?
To avoid any further disputes that could in the long term undermine its broader Indo-Pacific strategy, Paris should develop and promote co-management agreements, similar to the one proposed regarding Tromelin in 2010 and once imagined with Madagascar in 2019. These agreements seem to be the least controversial and most sustainable solution for France to maintain influence in the region.