High Quality Content by WIKIPEDIA articles! The Invasion of Cayenne was a combined military operation by an Anglo-Portuguese-Brazilian expeditionary force against Cayenne, capital of the French South American colony of French Guiana in 1809, during the Napoleonic Wars. The operation was part of a series of attacks on French held territory in the Americas during 1809 and due to commitments elsewhere, the British Royal Navy was unable to send substantial forces to attack the fortified river port. Instead, appeals were made to the Portuguese government, which had been driven out of Portugal the year before during the Peninsula War and was resident in Brazil. In exchange for providing troops and transports for the operation, the Portuguese were promised Guiana as an expansion of their holdings in Brazil for the duration of the conflict.