The War of 1812 began on June 18, 1812, when the United States declared war on Great Britain. Key reasons included British interference with American trade, the impressment of American sailors into the British Navy, and British support of Native American resistance to U.S. expansion. The war was fought on land and sea across North America. Though there was no clear winner, the war boosted American nationalism and confirmed U.S. independence. It ended with the Treaty of Ghent in 1814.