The War of 1812 was a conflict initiated by the United States against the United Kingdom and its allies fought mainly in North America and at sea during the wider Napoleonic Wars. The United States declared war on Britain on 18 June 1812. Although peace terms were agreed upon in the December 1814 Treaty of Ghent, the war did not officially end until the peace treaty was ratified by the United States Congress on 17 February 1815.