President Madison's declaration of war against Great Britain in 1812 was not popular with many Americans, especially when the first year of conflict brought a series of shattering American defeats. New England was in a virtual state of secession; the governor of Vermont ordered the state militia to resign from national service; and in Massachusetts there was talk of negotiating a separate peace with the enemy.

After threatening for a year, the British actually attacked the capital in August 1814.…