The War of 1812 was the first major war fought by the United States under the Constitution. It was also the second and last time that the nation waged war against Great Britain. The contest was a direct outgrowth of the Napoleonic Wars (1803–1815). The United States went to war to force the British to give up the Orders-in-Council, which regulated American trade with the European Continent, and impressment, which was the Royal Navy's practice of removing seamen from American merchant ships on the high seas.

The United States declared war on June 18, 1812, after little preparation. The congressional vote was relatively close: 79 to 49 in the House and 19 to 13 in the Senate. Declaring war against a major power after such limited preparation and against the wishes of a large minority of the American people was decidedly risky. Jeffersonian Republicans were willing to take this risk because they were confident...