The beginning of the war of 1812, happened, because in a war between Britain and France, the British decided to begin impressment, the act of basically turning nearby merchants into slaves for the navy. Another reason to happen, was that both France and the British, happened to try and block trading from america to the other country.
Due to this, there was a lot of political infighting in the american government, to whether or not they should go to war. but in a good thing, this infighting also ended the embargo act, which happened in 1809, but that led to the non-intercourse embargo, which simply stopped american traders from trading with the French and British. This proved not worth it, as, a mere year later, they repealed it.
Along with those things, there were a great many offensives taken against the Indians, mainly up in the north, where good land was, even if it was cold, but after a major battle, the Indians decided that they needed British help.