The History of Heated Shot

For as long as man has both wanted to kill other men and known that there was such a thing as fire, he has endeavored to combine the two. Various attempts to immolate an enemy from a distance have been recorded by history:
  • Britons launched heated clay balls into the tents of the invading Romans in 54BC.
  • Greek Fire, a sulphur/and/or/petroleum-based weapon developed in the 7th century, contributed to the naval invincibility of the Byzantine Empire for hundreds of years.
  • Arrows tipped with flame and catapult-delivered burning carcasses were used in Europe in Medieval siege warfare, and in the Middle East during the Crusades.
The first successful use of heated cannonballs, however, came about during the Siege of Polotsk in 1579.

The Siege of Polotsk, 1579. Click on the image for the full-sizer, and note the flying, flaming cannonballs on the left side of the picture
For it was during this siege that Stephen Báthory (1533-1586), leading the forces of the Grand Duchy of Lithuania, took the city of Polotsk (today in the nation of Belarus) from the Russians. This feat was achieved, in part, by lighting the defender's works on fire with the aforementioned heated shot, no doubt to much Russian consternation.

The HMS Juno, a Royal Navy fifth-rate. Please note that this ship was not involved in the hotshot-related action at the Battle of Yorktown: There appears to be no picture available of the HMS Charon, which is the ship involved, and which was also a fifth-rate. Again: This is not the Charon. Please return to your seats.
The method by which solid iron cannonballs were heated before the advent of the Hot Shot Furnace was over an open fire, atop metal grates. This was the way heated shot was accomplished for the first two centuries of its existence; A slow, dangerous and wasteful method. Dangerous for those employing it or not, this new tool of warfare was met with much enthusiasm by just about every European nation-state with artillery.
In what was perhaps the primary event that convinced America that heated shot was an effective defensive tool, the 44-gun British frigate HMS Charon was set aflame and destroyed by heated shot on October 10, 1781, at the Siege of Yorktown, during the American Revolutionary War (1775-1783). This heated shot was fired by the French, from a battery at what is today called French Trench, on the south bank of the York River.

An iron grate used by the British to heat shot during the Siege of Gibraltar, 1779-1783.
In September of 1782, France and Spain attempted to take advantage of Great Britain's discomfiture in the ongoing American Revolution by taking Gibraltar. This unsuccessful endeavor played out as a siege lasting over three years, but its opening act was a planned massed assault of over 50,000 French and Spanish troops, which was foiled by...heated shot!
The French and Spanish built ten ingenious, invincible floating batteries, with which they intended to pulverize the British defenses before the main assault. These timber structures, however, were easy prey for heated shot. British artillery destroyed three of these batteries, and heavily damaged the rest.

Austria utilized heated shot during their unsuccessful siege of the French city of Lille in 1792. This siege only lasted eight days, and the Austrians' use of modern superweapon heated shot against the city raised howls of "war crime!!" from the French Republican press.

Fewer than ten heated shots, fired by American gunboats at the Battle of Negro Fort in July of 1816, were needed to find the fort's powder magazine, detonating in what must have been a disturbing mess of dismembered limbs. Runaway African-American slaves and their Indian allies had been defending the fort at the behest of the British at the tail end of the War of 1812 (1812-1815) least until the fort blew up.

French and Spanish ships exploding at the Siege of Gibraltar: Thank you, heated shot!
The first examples of a dedicated Hot Shot Furnace, such as we would recognize today, were built by the French. Coastal batteries at the mouth of the Rhône River deflected British naval excursions in 1794, with a steady stream of expertly heated, red-hot shot.

So it has been comprehensively established that heated shot was an excellent means by which to destroy wooden ships. How great would it be, thought late-18th-century military theorists, if ships could also wield this devastating weapon? Counterintuitive? Absolutely! Did it work? Occasionally!

The French Romaine-class frigate, Incorruptible
France, Great Britain and the United States all experimented with some form of heated shot on their warships. The French Romaine class was a series of frigates designed in 1794. Originally called frégate-bombarde, or bomb frigates, each of these nine ships originally had a 12" mortar mounted in an unlikely fashion on a turntable immediately in front of its mizzen-, or rearmost, mast. They also featured a Hot Shot Furnace, which was swiftly determined to be impracticable and ridiculously dangerous, and removed.

The USS Constitution, launched in 1797, is an American 44-gun frigate known as "Old Ironsides" for its heroic exploits during the War of 1812. The Constitution occasionally fired heated shot during shore bombardments. The ship had no dedicated furnace, instead heating cannonballs in the galley stove.

The CSS Virginia, also known as the Merrimack, was one of the first ironclad warships, built by the Confederate States of America during the first year of the American Civil War (1861-1865). The Virginia's two amidships 9-inch Dahlgren guns were fitted out to fire heated shot, as they were the guns closest to the steamship's boilers, in which the shot was heated.

During the Battle of Hampton Roads (March 8-9, 1862), the Virginia had caused the USS Congress to run aground and, after trading shots for an hour, surrender. The Congress' crewmen were being ferried from their vessel when a Union battery on the harbor's northern shore opened fire on the Virginia. Viewing this as a flagrant breach of the protocols of war (?!), Commodore Franklin Buchanan, captain of the Virginia, ordered heated shot to be fired into the surrendered Congress by way of retaliation. That this was the Virginia's only use of heated shot during the battle suggests that heated shot was not only a rather inconvenient and unnecessary weapon under the circumstances, but also that it was considered to be a particularly terrifying one.

Battery B's Hot Shot Furnace at Fort Knox, Prospect, Maine
Hot Shot Furnaces were built at a few of America's Second System coastal forts just prior to the War of 1812, particularly those protecting the water approaches to New York City.

Simon Bernard (1779-1839), a French military engineer who had worked closely with Napoleon (1769-1821), came to the United States in 1816 to take part in the Board of Engineers. This association toured the eastern and gulf coasts of the US, and in 1821 presented a plan of coastal fortification to congress. The many lovely forts that came about as a result of this period are known as the Third System of US coastal fortification.

Simon Bernard of the Napoleonic Fancypants Brigade
Bernard was also responsible for the design of many of the Third System's signature forts, such as Fort Monroe, Fort Adams and Fort Pulaski. One of the many fortification ideas that Bernard brought with him to the US was a strong belief in the utility of heated shot. Under his direction, many of the forts built in the US during the era from the 1820's to the US Civil War were furnished with Hot Shot Furnaces.
To the best of our knowledge, none of these American furnaces ever turned out hot shot that was fired in anger. In some cases, the fort-building process was so slow that by the time a fort's guns were installed, they were far different from those which had originally been planned...and unable to fire heated shot.

In the case of Fort Knox on the Penobscot River at Prospect, Maine, two Hot Shot Furnaces were built in the 1840's to supply red-hot balls for 32-pounder cannons at that fort's two water batteries. By the time guns were actually supplied to Fort Knox in 1869, however, the 32-pounder cannons of the 1840's had been replaced in the US arsenal by 10- and 15-inch Rodman Guns, which didn't need to fire heated shot, so devastating was their calibre.

There is a distinct possibility that heated shot might have been fired at the US Navy from Confederate-held Fort Macon in 1862. When a Union blockading squadron approached Fort Macon in the morning of April 25, 1862, it is likely that the fort's two Hot Shot Furnaces were fired up and ready for action. Whether any red-hot shot was flung at the Union ships went unrecorded by history, but it wouldn't have made any difference if it had, because the modern, rifled cannon brought to bear against the Confederates far outranged the Model 1841, Navy 32-pounder smoothbores mounted at Fort Macon...and the US Navy was smart enough to stay well out of the Confederates' range as it pounded the fort into the ground. For the full story of Fort Macon, please visit the Fort Macon page at!

Fort Macon at Beaufort, North Carolina. The arrow in the fort's center points out the reproduction Hot Shot Furnace that exists there today, while the smaller arrow to the left illustrates the likely location of the fort's second shot furnace. Both of Fort Macon's original Hot Shot Furnaces were demolished in 1867.

A mobile Hot Shot Furnace of the Norwegian Navy, circa 1860
While the United States was busily building numerous brick, sandstone and/or coquina Hot Shot Furnaces in the 1840's, similar furnaces were being built in France: At least three Hot Shot Furnaces of familiar design still exist in Cannes and Plévenon, France.

Other European nations experimented with mobile Hot Shot Furnaces into the 1860's, but weapons technology was already surpassing the need for heated shot. A molten iron shell was introduced by the Royal Navy in 1860, a means by which 26 pounds of molten iron could be delivered from muzzle-loading 68-pounder guns on such ships as the HMS Warrior, Great Britain's first iron-hulled, armored warship.

But even such brilliant(ly impractical) innovations as the molten iron shell were rendered unnecessary by the advent of huge explosive shells, fired from guns with increasingly long range and incredible accuracy.

Captain Addison's Hot Shot Furnace, a British design introduced in 1846.
Heated shot existed because of its utility against the wooden warship. Once the world's navies noted such ironclads as the USS Monitor, CSS Virginia and the first oceangoing ironclad, France's Gloire (launched in 1867), the days of the wooden-hulled battleship were over. Most Hot Shot Furnaces were dismantled, their heroic visage suddenly unsightly and purposeless. Who knows how many Hot Shot Furnaces once sat upon this earth? We will do what we can to celebrate those that are left.
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