The most visible expression of seapower was the battleship. From the emergence of this distinctly strongly built and heavily armed type of warship during the first half of the seventeenth century, naval power was measured by the number of these vessels a state possessed. Typically, at the height of their power in the eighteenth and early nineteenth centuries, these three-masted, square-rigged vessels carried between 60 and 120 cannons in broadside batteries. From the 1650s, the English, Dutch, Swedes, Danes and French were well aware that squadrons of these ships had the greatest diplomatic impact.
The dominance of the world’s oceans by the British Royal Navy, which first outbuilt and then outfought its enemies with battleships, proved that seapower was measured by the battleship. The reality, as usual, is rather more complicated than this. To the seventeenth- and eighteenth-century mind the role of seapower and the advantages of battleships were less obvious. The dominance of the battleship was based on its ability to appear in almost all the waters of the world in sufficient numbers for a long enough period to overwhelm local naval resistance. By the end of the Napoleonic Wars in 1815, British battleships dominated most oceanic sea routes by concentrating on the terminal points of these routes. They prohibited equal concentrations of potentially hostile men-of-war and allowed a variety of smaller vessels to exploit the advantages of sea communications.
Since the sixteenth century, the heavily armed sailing warship was seen as a floating castle, impregnable except by another similar ship. Their size and firepower forced smaller, less well-armed vessels to keep at a discrete distance. Because the range of smoothbore cannon was very limited, even ships of equal force and size found it difficult to concentrate overwhelming firepower upon an individual enemy vessel. These ships could also absorb a fearful pounding from the iron cannonballs. With two or more enemy vessels around a warship, dividing the fire of defenders and restricting their manoeuvrability, a warship might be overcome by gunfire or boarding. By the 1650s the English were building their vessels rather larger and with a higher ratio of guns per ton than their Dutch rivals, but in all countries there was a general consolidation of the warship at under 1,000 tons and capable of carrying between 30 and 80 guns of different sizes. There was a great variety within this definition as the ability of merchant vessels to fight alongside purpose-built warships was still important when the principle tactic was to close and board the enemy in a melée. By the time the line of battle was firmly established as the standard tactical formation during the 1660s, lighter merchant ships and lightly armed warships became less able to sustain their place in a pitched battle, leaving the centre stage to the purpose-built line-of-battle ship ranging eventually up to 2,000 tons and carrying 120 large cannon.
Liners, battle ships of the line, or line-of-battle ships were the most powerful ships of the age of fighting sail. These ships were expensive, complex, and heavily armed and manned, and they carried great national prestige. Ships of the line ushered in the concept of the capital ship.
As gunfire supplanted boarding and the ram in naval warfare, it began to dictate naval tactics. Naval architects learned that heavy cannon were best positioned within a hull rather than mounted on deck or in ungainly castles built on the bow and stern. Locating the heavy guns within the hull balanced the vessel while keeping a low center of gravity. Since a ship’s most powerful battery lay at its sides, the most effective tactic in battle was to bring these sides to bear in a devastating broadside.
During the seventeenth and eighteenth centuries the largest warships acquired more than one gun deck and could accommodate up to 100 guns. When operating in tandem or in squadrons, the natural tactic was to form a line in order to expose the maximum number of guns to any potential enemy and protect the vulnerable, lightly armed bow and stern. Fleets during this time typically fought each other in matching line-ahead formations, exchanging broadsides. Line-ahead tactics dictated that the vessels in the formation be the most powerful ships available, for any ship casualty or break in the line could expose the ships ahead and astern of the break to end-on fire.
By the seventeenth century, France vied with Spain, England, and the Netherlands for control of the seas. King Louis XIV hungered for maritime commerce and naval power, and his finance minister and minister of the navy Jean Baptiste Colbert did his best to satisfy those desires. From 1661 until his death, in 1683, Colbert increased the size and number of French warships, improved training of naval officers, and ordered numerous charts prepared for better navigation. In 1666, he founded the Académie des Sciences, which became a forum for scientific matters, including navigation and ship design. In 1680 Colbert brought together prominent French shipbuilders to determine the best way to maximize speed, maneuverability, and gun positioning on board men-of-war. This group established standard dimensions for each class of warship and eliminated many of the rule-of-thumb methods practiced by private contractors.
During the 1700s Colbert’s campaign to promote navigation and shipbuilding bore fruit in the form of design research. French experimenters pioneered the use of model ship basins to test the performance of ship forms. In addition, the Académie awarded prizes for research on ship design subjects, such as the best method for diminishing the rolling and pitching of vessels or propelling a vessel without the use of sails.
French works on naval architecture became recognized as the world’s leading ship design treatises. Paul Hoste, a Jesuit professor at the Toulon Naval Academy, wrote Théorie de la construction des vaisseaux in 1697. His treatise laid the foundation for later works on naval architecture by employing the principles of statics and mechanics. In 1746 Pierre Bouguer completed his influential work, Traité du navire. Bouguer devised the trapezoidal rule for the mensuration of areas, which became the basis for many of the hydrostatic calculations that enter into modern naval architecture. In 1752, naval architect and instructor Duhamel du Monceau published Elémens de l’architecture navale. Monceau’s book became widely recognized as one of the eighteenth century’s best naval architecture treatises and was translated into Dutch, German, and English.