in 1965, the united kingdom split the chagos archipelago from mauritius and the islands of aldabra, farquhar and desroches (des roches) from the seychelles to form the british indian ocean territory. the purpose was to allow the construction of military facilities for the mutual benefit of the united kingdom and the united states. the islands were formally established as an overseas territory of the united kingdom on 8 november 1965. on 23 june 1976, aldabra, farquhar and desroches were returned to seychelles as a result of its attaining independence. subsequently, biot has consisted only of the six main island groups comprising the chagos archipelago.