What was the british policy of impressment?

When His Majesty's Service needed men, detachments were sent out to bars, night clubs, and etc. and able bodied men were pressed (taken) into Her Majesty's service. Prior to the War of 1812 (1812 to 1814); the British boarded US vessels at sea and pressed into service (took by force) US abled bodied males for duty upon Royal Navy Warships (Men 'O War). These men were former British seamen who had jumped ship, by the thousands, while in the service of the Royal Navy in the war against the Napoleonic Empire and were considered to be deserters. The US government then considered them to be US citizens, but the Royal Navy adhered to a principle of inalienable British citizenship and seized the seamen back. This was one of the causes of the War of 1812.