The War of 1812 (18121815) was a conflict fought between the United States, the United Kingdom, and their respective allies. Historians in Britain often see it as a minor theater of the Napoleonic Wars; in the United States and Canada, it is seen as a war in its own right. 

Since the outbreak of war with Napoleonic France, Britain had enforced a naval blockade to choke off neutral trade to France, which the United States contested as illegal under international law. To man the blockade, Britain impressed American merchant sailors into the Royal Navy. Incidents such as the "Chesapeake–Leopard" Affair inflamed anti-British sentiment. In 1811, the British were in turn outraged by the "Little Belt" Affair, in which 11 British sailors died. British political support for a Native American buffer state, which conducted raids on American settlers on the frontier, hindered American expansion. On June 18, 1812, President James Madison, after receiving heavy pressure from the War Hawks in Congress, signed the American declaration of war into law. Senior figures such as Lord Liverpool and Lord Castlereagh believed it to have been an opportunistic ploy to annex Canada while Britain was fighting a war with France. The view was shared in much of New England.
Who was it between?
he United States, the United Kingdom, and their respective allies