Wiki quoting Mahan:_In the early to mid-17th century, several navies, particularly those of the
Netherlands and England, began to use new fighting techniques. Previously battles had usually been fought by great fleets of ships closing with each other and fighting in whatever arrangement they found themselves in, often boarding enemy vessels as opportunities presented themselves. As the use of
broadsides (coordinated fire by the
battery of
cannon on one side of a
warship) became increasingly dominant in battle, tactics changed. The evolving
line-of-battle tactic, first used in an ad hoc way, required ships to form single-file lines and close with the enemy fleet on the same tack, battering the enemy fleet until one side had had enough and retreated. Any manoeuvres would be carried out with the ships remaining in line for mutual protection.
In order that this order of battle, this long thin line of guns, may not be injured or broken at some point weaker than the rest, there is at the same time felt the necessity of putting in it only ships which, if not of equal force, have at least equally strong sides. Logically it follows, at the same moment in which the line ahead became definitively the order for battle, there was established the distinction between the ships 'of the line', alone destined for a place therein, and the lighter ships meant for other uses.
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