 Since the beginning of the Napoleonic Wars in 1803 , French privateers and naval frigates operating from the fortified island bases of Île de France and Île Bonaparte had attacked British shipping in the Indian Ocean . The huge distances involved , restrictions on supplies and the presence of Royal Navy warships and heavily armed East Indiamen had prevented these relatively weak French ships from attacking the convoys that transported millions of pounds worth of goods from British India and the Far East to the United Kingdom . When one French squadron under Admiral Linois had tried to seize a convoy in 1805 , it had been driven off by the aggressive tactics of the merchant captains . 
