My mother asks “What exactly was the War of 1812 about? How did it start?”
The War of 1812, which lasted until 1815, was the only part of the whole mess with Napoleon that actually reached our borders. There was no one main reason why we started fighting with Canada, it was more a sum of several irritations and fears, including American ships and sailors being forced into the British navy and rumors that Great Britain would support an independent Indian state in the Midwest, which would naturally not mesh well with American expansion.
The war began in June 1812, when James Madison sent a message to Congress saying, basically, “Man, the British are being total jackasses right now, aren't they?” Congress subsequently declared war on Great Britain, and prepared to attack Canada; it is worth noting that the states close to Canada opposed the invasion, though in Federalist New England this was likely due in part to an opposition to the Democratic-Republican James Madison. His critics labeled the conflict Mr. Madison's war, though when it became popular eventually that didn't work so well.
The hilarious thing was, at the beginning neither of us really had any troops to send to the front. Great Britain was busy with their war against France, and couldn't really spare any men for Canada, and the American army was roughly ten thousand guys. Congress authorized the recruitment of twenty thousand more, but nobody wanted to do it, and the militias that did exist were against invading Canada. The first real action was a month later, when the equivalent of a couple thousand guys with shotguns and pickup trucks surrendered Detroit to a mixture of British soldiers, Canadian volunteers, and Native Americans.
That hurt, obviously, as a major front in the Midwest, but once we actually started building ships in the Great Lakes, things went a bit better, and once the Native American leader Tecumseh was killed in battle all unity in that area ceased. Unfortunately, while we had ships in the Great Lakes, we didn't have much of a navy on the actual coast, which is how Washington, among other cities, was sacked, the source of the Star-Spangled Banner song.
After Napoleon gave up in 1814, the major European conflict ended, and Great Britain could send over their main forces, but by that point we'd actually figured out what the hell we were doing, and they didn't have much luck. At that point, the major things that had caused the war were no longer an issue, and neither side had any decent prospects of a significant victory, so we agreed to just end the war, with no concessions made by either side. America regarded it as a win because we'd defended ourselves against foreign threats, and Canada had largely the same opinion; this was actually the first time that residents of the area started thinking of themselves as Canadians.
After the Treaty of Ghent was signed, the US and Great Britain got along pretty well, resuming normal trade and diplomatic relations, and developing the root of the Special Relationship we have today, where the UK is perhaps our staunchest ally. It seems rather strange to become allies almost immediately after a war, but the grievances were not that severe, and once they went away the normal strategic advantages of being close to Great Britain resumed their previous importance.
A few other things of note in this war: the effective end of the Federalist Party as an organized force in politics, in part because of their opposition and their backing of threatened secessions in New England; the exploits of Generals William Henry Harrison and Andrew Jackson and Major Zachary Taylor, all of whom were later elected President; the decline of Native American fortunes, both in the death of the leader and in the loss of support from the British.
