The War of 1812 was caused by three grievances that the United States held toward Great Britain. The first two, the imposition of trade restrictions and forced recruitment of American sailors to the Royal Navy, were the result of broader British geopolitical interests, yet they ultimately affected America acutely. The final cause, Britain's arming of certain Native Americans, related directly to American ambitions for territorial expansion.
Many of the roots of the War of 1812 originate in the British struggle against France under Napoleon. By 1812, the British had been at war with the French emperor on and off for nearly a decade. Because Napoleon's ambitions to invade England had been foiled by British naval power, he resorted to economic warfare by stifling England's European trade through his Continental System. Consequently, Britain tried to weaken French trade, in part by imposing restrictions upon the United States.
Additionally, Britain tried to bolster its navy by forcing into service men they seized from American merchant vessels, an action that outraged the American public and leaders. Regarding Native Americans, the United States accused Britain of arming tribes already hostile to American settlement along the western frontier.
In the two years before the War of 1812, circumstances surrounding these three grievances intensified. For example, by 1810, after Napoleon hinted that he might end his own trade difficulties with America, President James Madison ended all commerce with Britain. Throughout 1811, conditions along the frontier also rapidly deteriorated, ultimately resulting in all-out battle under future president William Henry Harrison at Tippecanoe that fall. By the beginning of 1812, pro-war voices in Congress, called the "War Hawks," gained the upper hand, and Congress finally declared war against Britain on June 1. The war ended in 1815 with American victory.