Article: By far the largest military action in which the United States engaged during this era was the War of 1812. With Britain locked in a major war with Napoleon's France, its policy was to block American shipments to France. The United States sought to remain neutral while pursuing overseas trade. Britain cut the trade and impressed seamen on American ships into the Royal Navy, despite intense protests. Britain supported an Indian insurrection in the American Midwest, with the goal of creating an Indian state there that would block American expansion. The United States finally declared war on the United Kingdom in 1812, the first time the U.S. had officially declared war. Not hopeful of defeating the Royal Navy, the U.S. attacked the British Empire by invading British Canada, hoping to use captured territory as a bargaining chip. The invasion of Canada was a debacle, though concurrent wars with Native Americans on the western front (Tecumseh's War and the Creek War) were more successful. After defeating Napoleon in 1814, Britain sent large veteran armies to invade New York, raid Washington and capture the key control of the Mississippi River at New Orleans. The New York invasion was a fiasco after the much larger British army retreated to Canada. The raiders succeeded in the burning of Washington on 25 August 1814, but were repulsed in their Chesapeake Bay Campaign at the Battle of Baltimore and the British commander killed. The major invasion in Louisiana was stopped by a one-sided military battle that killed the top three British generals and thousands of soldiers. The winners were the commanding general of the Battle of New Orleans, Major General Andrew Jackson, who became president and the Americans who basked in a victory over a much more powerful nation. The peace treaty proved successful, and the U.S. and Britain never again went to war. The losers were the Indians, who never gained the independent territory in the Midwest promised by Britain.

Question: What conflict caused Britain to blockade trade?
a major war with Napoleon's France