 The French Indian Ocean territories of Île de France and Île Bonaparte were heavily fortified island bases from which French frigates were able to launch raids against British trade routes across the Indian Ocean during the Napoleonic Wars . In late 1808 , a squadron of four frigates departed France for the region under Commodore Jacques Hamelin with orders to prey on the convoys of East Indiamen that regularly crossed the Indian Ocean . During the late spring of 1809 , these frigates dispersed into the Bay of Bengal , attacking British shipping and coastal harbours around the rim of the Eastern Indian Ocean . The Royal Navy was also preparing an operation in the region , a staggered campaign intended to blockade , isolate and subsequently capture both Île de France and Île Bonaparte , eliminating the final French territories and bases east of Africa . 
