A merchant navy or merchant marine is the fleet of merchant vessels that are registered in a country. Seafarers on merchant vessels of various ranks and sometimes members of maritime trade unions, are required by the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers to carry Merchant Mariner's Documents. King George V bestowed the title of the "Merchant Navy" on the British merchant shipping fleets following their service in the First World War;