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.