Until the mid-17th century, the tactics of a fleet were often to "charge" the enemy, firing bow chaser cannon, which did not deploy the broadside to its best effect. These new vessels required new tactics, and "since ... almost all the artillery is found upon the sides of a ship of war, hence it is the beam that must necessarily and always be turned toward the enemy. On the other hand, it is necessary that the sight of the latter must never be interrupted by a friendly ship. Only one formation allows the ships of the same fleet to satisfy fully these conditions. That formation is the line ahead . This line, therefore, is imposed as the only order of battle, and consequently as the basis of all fleet tactics."