18 June 1812: The USA declared War on Britain and Ireland:

An Act Declaring War Between the United Kingdom of Great Britain and Ireland and the Dependencies Thereof and the United States of America and Their Territories.


Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled, That war be and the same is hereby declared to exist between the United Kingdom of Great Britain and Ireland and the dependencies thereof, and the United States of America and their territories; and that the President of the United States is hereby authorized to use the whole land and naval force of the United States to carry the same into effect, and to issue to private armed vessels of the United States commissions or letters of marque and general reprisal, in such form as he shall think proper, and under the seal of the United States, against the vessels, goods, and effects of the government of the said United Kingdom of Great Britain and Ireland, and the subjects thereof

APPROVED, June 18, 1812

The War of 1812 was a military conflict fought between the forces of the United States of America and those of the British Empire. The Americans declared war in 1812 for several reasons, including trade restrictions brought about by Britain's ongoing war with France, the impressment of American merchant sailors into the Royal Navy, British support of American Indian tribes against American expansion, outrage over insults to national honour after humiliations on the high seas and possible American desire to annex Canada.

The War of 1812 formally began on June 18, 1812, when President James Madison signed the this act into law.