The Atlantic campaign of 1806 was a complicated series of manoeuvrees and counter-manoeuveres conducted by squadrons of the French Navy and the British Royal Navy across the Atlantic Ocean during the spring and summer of 1806, as part of the Napoleonic Wars. The campaign followed directly from the Trafalgar campaign of the year before, in which the French Mediterranean fleet had crossed the Atlantic, returned to Europe and joined with the Spanish fleet. On 21 October 1805, this combined force was destroyed by a British fleet under Lord Nelson at the Battle of Trafalgar, although the campaign did not end until the Battle of Cape Ortegal on 4 November 1805. Believing that the French Navy would not be capable of organised resistance at sea during the winter, the First Lord of the Admiralty Lord Barham withdrew the British blockade squadrons to harbour. Barham had miscalculated – the French Atlantic fleet, based at Brest, had not been involved in the Trafalgar campaign and was therefore at full strength.