Britain's warships defeated the combined fleets of France and Spain off Cape Trafalgar in 1805. The most powerful British warships carried 100 or more cannons and had hulls that were reinforced with double-layered oak planks up to 46 cm (18 in) thick. These ships, called ships of the line, served on the front lines of maritime battles.
Sail-powered naval warfare climaxed from 1650 to 1840. During this period, ships carried heavy artillery to destroy their opponents-as many as 100 cannons, most placed in gun ports on the sides of the vessel. To accommodate the cannons, which could fire only straight out to the side of the vessel, warships fell into position in long orderly lines. The enemy usually lined up in the same formation and battle commenced, broadside against broadside.
This battle configuration earned the warships powerful enough to fight on the front lines of battle the name ships of the line. From the 17th century, British warships were rated in six classes, according to the number of guns they carried. Ships of the line claimed the highest ratings. First-rate ships had three gun decks with over 100 guns. Third-rate battleships with 60 guns or more were typically the lowest-rated vessels used as ships of the line by the British navy. In rare cases, fourth-rate ships, which had between 40 and 60 guns, served as ships of the line. Other navies used similar rating systems.
Ships of the line increased in size and firepower during the years that they were popular. In the mid-17th century the largest ships of the line reached 1,500 tons. By 1750 ships of 2,000 tons or more were common, and by 1800 ships of the line usually exceeded 2,500 tons. The hulls of these massive warships were often reinforced with double-layered oak planks up to 46 cm (18 in) thick. Such construction required unprecedented amounts of wood. For example, about 2,500 mature oak trees were used to build HMS Victory, Britain's flagship at the famous Battle of Trafalgar in 1805. This superlative ship featured 32 km (20 mi) of rope and had a crew of 850 sailors and marines.
Like the East Indiamen merchant ships, ships of the line often served as monuments to the powers that built them. In many cases, no cost was spared in their construction. They were highly decorated with woodcarvings and featured officers' quarters designed for comfort and elegance. Such luxuries were not extended to all the sailors, however. Most of the crew slept in hammocks suspended from beams on the gun decks.