By the middle of the 17th century, warships were carrying increasing numbers of cannon on three decks. Naval tactics evolved to bring each ship's firepower to bear in a line of battle—coordinated movements of a fleet of warships to engage a line of ships in the enemy fleet. Carracks with a single cannon deck evolved into galleons with as many as two full cannon decks, which evolved into the man-of-war, and further into the ship of the line—designed for engaging the enemy in a line of battle. One side of a ship was expected to shoot broadsides against an enemy ship at close range. In the 18th century, the small and fast frigate and sloop-of-war—too small to stand in the line of battle—evolved to convoy trade, scout for enemy ships and blockade enemy coasts.