The Continental Blockade and the 'Spanish Ulcer'

Unable to defeat Britain militarily after Trafalgar, Napoleon turned to economic warfare. The Berlin Decree of 21 November 1806 formally established the Continental Blockade, prohibiting states under French influence from trading with Britain and its colonies, and Napoleon reinforced it with the Milan Decree of December 1807. Portugal's refusal to fully join the blockade, because of its close commercial ties with Britain, directly triggered a French invasion in 1807: under the Treaty of Fontainebleau, French troops crossed Spain, General Junot occupied Lisbon in November 1807, and the Portuguese royal family fled to Brazil escorted by the British fleet.