The practice of forcing sailors into naval service that helped spark the War of 1812 was impressment.
Britain’s Royal Navy used press gangs and shipboard searches to seize men, officially seeking British deserters and subjects. British officers also removed American sailors, including some native-born citizens, because nationality was often difficult to prove at sea. The policy angered Americans who regarded it as an assault on national sovereignty and individual liberty.
Impressment was one of several causes of the war, alongside British interference with U.S. trade, restrictions connected to the Napoleonic Wars, and frontier conflict involving Native nations supported by Britain. The 1807 Chesapeake–Leopard affair intensified American outrage after a British warship attacked and boarded the USS Chesapeake.
A common mix-up is confusing impressment with privateering or a blockade. Privateers were privately owned vessels authorized to attack enemy shipping, while a blockade restricted access to ports. Impressment specifically meant compelling people into naval service. The slogan “Free Trade and Sailors’ Rights” captured the American protest.