The term "frocking" dates back to the Age of Sail, when communications between the Department of the Navy and ships at sea could take months. News of the promotion of an officer arrived, usually via letters brought by another ship, and often with orders for the newly promoted officer to report to a new ship or station. The ship that brought the news would often take that officer away to his new post. Since the departing officer created a vacancy on the first ship, the captain would often forward a recommendation for promotion for one of the remaining officers, which was to be carried back to the Department of the Navy.