Impressment is the act of kidnapping people to serve as sailors. It was much used by the Royal Navy during the 18th century and early 19th century as a means of crewing warships. The Royal Navy impressed many British and American sailors during the 1700s and the early 1800s.
Conditions for the average sailor in the Royal Navy were very bad, and pay was low. Especially during wartime, it was impossible to fully staff the Navy with volunteers, a problem worsened by desertion. The Impress Service was formed to force sailors to join the navy, based legally on the right of the King to call men to military service. The Impress Service in turn utilized "press gangs" to do the convincing, duping, kidnapping, or otherwise forcing sailors into Navy service. Corruption was rife, as press gangs could be bribed in order to bypass a "candidate".
Impressment was criticized as oppressive and unjust, but was tolerated for over a century in Britain.
In the early 1800s, the Royal Navy started to aggressively reclaim British deserters posing as Americans, both by halting and searching American merchant ships, and by searching American port cities. Since it was difficult to tell whether a sailor was British or American, the Royal Navy "accidentally" impressed over 6000 American sailors during the early 1800s. This was one of the factors leading to the War of 1812 in North America.
British impressment ended after 1815.