How were shore bombardments carried out during the Age of Sail? Did the ships sail past firing, merely haul up their sails, coast to a stop and begin firing, or did they anchor before opening fire?
If they anchored, then how did the ships anchor themselves so that their guns face the shore?
While I’ve contributed on occasion to answers prior to today, this is my first effort at responding directly to an Ask Historians question.
How ships were built:
During the Age of Sail, basically the mid-17th to mid-19th century, early shore bombardment was accomplished by ships called Bomb Vessels. These vessels were historically a French invention and later perfected by the British and United States navies and other nations. An early French example was short in length and broad in beam making for a stable gun platform, like a raft is inherently stable. Five of these ships were deployed by the French to shell Algiers in 1681. However, a much earlier recorded example was at the siege of Calais in 1347, whereby England’s Edward III used bomb-ships fitted with bombardes, a type of mortar. Bomb ships were built enormously strong and had a low freeboard or distance from the deck to the waterline which made them susceptible to foundering. Reinforced ribbing was needed to sustain the shock from the repeated discharges from the motars.
These shore bombardment vessels went by other names and incorporated different type designs. For example, in 18th century England they were called bomb ketches. The ketch was a two-masted square-rigged ship with it’s mainmast located close to midships and mizzen aft but lacking in a foremast so that the forward area of the ship was clear for the firing of mortars. Bomb ketches were around 100 tons and 60 to 70 feet in length having a shallow draft of 10 feet or so, permitting maneuvering close to shore and carried two mortars, a 13-inch and a 10-inch. In the 19th century, these vessels grew to 300 tons and to 90 feet in length.
During the Tripoli campaign in 1804 and Mexican American War, the US Navy used bomb vessels carrying four 10-inch mortars. The US Navy also employed schooners which carried 13-inch mortars during the American Civil War.
How they were fought:
These bomb vessels were intended for shore bombardment for attacking facilities ashore and not to fight against other ship. As mentioned, these ships were equipped with mortars which is similar to a cannon but having a large bore and a short barrel. The mortars fired their projectiles at a high angle, typically 45 degrees or greater. These projectiles were perforated containers containing combustibles and were ignited by the explosion of the propellant charge. They were particularly well suited for attacking targets protected by heavy walls, including the use of indirect fire where combustible shells were lobbed over and into fortifications. Depending on mortar size, amount of propellant and degree of inclination, ranges would vary from 1,000 to 4,000 yards from the intended target.
Bomb ketches were not designed to be good sailing ships due to the placement of masts for clear fields of fire from the mortars which were mounted on the vessel’s centerline. Once in position, these bomb ketches would anchor up in order to fire accurately, making them easy targets for return fire from shore batteries. However, the British mounted the mortars on a rotating platform or barbette so that it was not necessary to reposition the entire vessel to change the aim or target.
Spencer Tucker. “The Navy Discovers Shore Bombardment" Naval History, Oct 1994.
Chris Ware “The Bomb Vessel: Shore Bombardment During the Age of Sail", Naval Institute Press. 1994.
A Global Chronology of Conflict: From the Ancient World to the Modern Middle East. Spencer Tucker, Editor. 2010.
To add to u/KapitanKurt's excellent reply on bomb vessels:
There were various ways in which sailing ships could bombard shore fortifications, which were of various effectiveness in different eras.
In 1509, the Portuguese won the critical Battle of Diu, against the combined fleets of the Ottomans, Mamluks, and various Indian sultanates, which gave them control of the Indian Ocean.
The combined fleet of the Mamluks, the Ottomans, the Sultan of Gujarat and the Zamorin of Calicut, amounted to 12 major ships (6 carracks and 6 galleys) and over 80 smaller local dhows.
Franciso assembled 5 large ‘naus’, four smaller ‘naus’, four ‘caravelas redondas’, two ‘caravelas’, two galleys and one ‘bergantim’, and sailed these 18 ships to Diu.
The Muslim fleet decided not to come out to attack the Portuguese, but to defend the harbor of Diu, protected by the cannon of the harbor forts.
Francisco sailed straight in with all guns blazing.
The entire Muslim fleet was destroyed or captured with great losses of sailors and soldiers. The harbor forts were reduced to rubble.
The powerful Portuguese ships, armed with larger cannon than the defenders, were able to destroy both the shore defenses and the Muslim fleet.
Later, it became more difficult for warships to defeat shore based forts. This was for three reasons:
The earth and stone or brick walls of shore forts gave more protection than the wooden sides of ships.
Shore based forts often mounted larger cannon than even ships of the line, giving them longer range and more destructive power.
Shore based forts often employed heated shot, which could set naval ships on fire. Ships could not safely deploy heated shot (because they were too flammable for this to be safe).
Bomb ketches were introduced to reverse this situation, and make it possible for naval forces to overcome shore based fortifications, by lobbing explosive shells over the walls of the forts and into their interiors.
This helped, but was not decisive. Shore based forts were still fairly often able to withstand an assault by bomb vessels. Witness the British assault on Fort McHenry, which defended the approaches to Baltimore during the War of 1812. As recorded in the American National Anthem, "The bombs bursting in air, The rocket's red glare, gave proof through the night that our flag was still there."
The assault by bomb vessels and Congreve rockets failed. When the British fleet, thinking they had defeated Fort McHenry, tried to head up the inlet to assault Baltimore, the big guns of the fort opened up, forcing the fleet to withdraw.
Bomb vessels shifted the balance a little towards naval forces vs. land based fortifications, but not decisively.
It took the combination of iron clad warships, armed with main guns which could fire exploding shells at a high angle in the American Civil War to decisively shift the balance.
In that war, naval fleets could usually count on being able to defeat shore based fortifications, though it was still not easy.