The British feared that Denmark would submit to French pressure to close the Baltic sea to British ships, damaging trade, closing off naval supplies, and shutting off access to Sweden and Russia. It was also feared they would join an alliance against Britain or capitulate easily to French invasion. A naval squadron was sent in July 1807 to observe the Danish and convince them to join a British alliance. The diplomatic mission failed and the British bombarded Copenhagen and its civilian population from 2-5 September, killing 2,000 people. An armistice was called for by the Danes on 5 September and they surrendered their entire fleet and naval stores two days later. Following this attack Alexander I declared war on the United Kingdom, resulting in the Anglo-Russian war (1807-12).

See Rory Muir, Britain and the Defeat of Napoleon, 1807-1815 (New Haven and London: Yale University Press, 1996), pp. 23-25.