The War Hawks were a group of Jeffersonian Republican politicians who advocated declaring war on Great Britain in the first decade of the 19th century. They were largely successful in persuading other members of Congress, and on June 18, 1812 the United States declared war on Britain.
The following war, known historically as the War of 1812, was fought for a number of reasons. At the time that war was declared, Britain was already locked into war with Napoleonic France, a historic ally of the United States. Britain had seized a number of American sailors, impressing them into service in the Royal Navy, and provoked Native Americans to attack U.S. settlements. The War Hawks argued that the British military was overextended, and significant territorial gains could be made in the British colonies of Canada.