The Berlin Decree was issued in Berlin by Napoleon on November 21, 1806, following the French success against Prussia at the Battle of Jena. The decree forbade the import of British goods into European countries allied with or dependent upon France, and installed the Continental System in Europe. All connections were to be cut, even the mail. Any ships who had been discovered trading with Great Britain were liable to French maritime attacks and seizures.
Napoleon's main goal was to control the trade of all European countries, without consulting their governments. The ostensible goal was to weaken the British economy by closing French-controlled territory to its trade, but British merchants smuggled in many goods and the Continental System was not a powerful weapon of economic war.
The Continental System eventually led to economic ruin for France and its allies. Less damage was done to the economy of Britain, which had control of the Atlantic Ocean trade. Other European nations removed themselves from the Continental System, which led in part to the downfall of Napoleon.
The Milan decree for the same purpose was issued the next year.