Ships of the line
- Ships of the line were 1st, 2nd, or 3rd-rated ships in the rating system of the Royal Navy.
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 (of battle) was a warship powerful enough to take a place in the battle line. (Another term, a "line of battle" ship, shortened to become a "battleship".) Generally, this meant a third-rate or larger ship, with guns on two or three (or in rare cases, four) decks. Rated ships smaller than this were frigates, which mostly carried all their guns on a single deck. European navies in particular used battleships to fight fleet actions which might last for days and involve over 100 ships.
In fiction
Isaac Asimov adapted the term "ship of the Line" to apply to the armed spaceships which served a similar role to the old naval vessels for the Galactic Empire of his Foundation trilogy, as mainstays of the space fleet.
