A model of a ship of the line. In the age of sail, after the development of the line of battle tactic in the mid 17th century, and up to the mid 19th century, a ship of the line was a warship powerful enough to take a place in the battle line. Another term, line of battle ship, was shortened to become "battleship", but this is a later usage and is not appropriate for the age of sail.
The fact that a ship would have to stand and fight its opposite number in the enemy line, whatever the size of the enemy ship, put a lower limit on the size of vessel which could be allowed into the line. Generally, this meant a third-rate or larger ship, with guns on two or three, or in rare cases, four decks...read more...