Coal torpedo The coal torpedo was a hollow iron casting filled with explosives and covered in coal dust , deployed by the Confederate Secret Service during the American Civil War , and intended for doing harm to Union steam transportation . When shoveled into the firebox amongst the coal , the resulting explosion would at the very least damage the boiler and render the engines inoperable . At worst , a catastrophic boiler explosion would kill crewmen , plus passengers , start a fire , perhaps , even sink the vessel . Development . The coal torpedo was invented by Capt . Thomas Edgeworth Courtenay of the Confederate Secret Service . During the Civil War , the term torpedo was used to indicate a wide range of explosive devices including what are now called land mine s , naval mine s , improvised explosive devices , and booby trap s . Northern newspapers referred to Courtenay ' s coal bombs as torpedoes , or sometimes " infernal machines " ; Courtenay himself called it his " coal shell " . The torpedoes were manufactured at the 7th Avenue Artillery shop ( across the street from Tredegar Iron Works ) in Richmond , Virginia , in January 1864 . The manufacturing process was similar to that used for artillery shells , except that actual pieces of coal were used as patterns for iron castings . The walls of the coal shell were about 3 / 8 inch thick , creating a hollow space inside sufficient to hold 3 – 4 ounces of gunpowder . After filling , the shell was closed with a threaded plug , then dipped in melted beeswax and rolled in coal dust , creating the appearance of a lump of coal . Finished coal torpedoes were about 4 inches ( 10 cm ) on a side and weighed 3 – 4 lb ( 1 . 5 – 2 kg ) . The size and powder charge of the coal torpedo was similar to a 6 pound Shrapnel shell ( a hollow , four - inch cannonball containing gunpowder and 24 musket balls as shrapnel ) or the equivalent of three Civil War - era hand grenades . Even so , the explosion of a coal torpedo under a ship ' s boiler would not by itself be sufficient to sink the vessel . The purpose of the coal torpedo was to burst the pressurized steam boiler , which had the potential to cause a tremendous secondary explosion . Boiler explosions were not uncommon in the early years of steam transportation , and often resulted in the complete destruction of the vessel by fire . In action , the coal torpedo would leave little evidence that a boiler explosion was due to sabotage . Deployment . Courtenay was authorized to form a company of men to infiltrate enemy lines and place coal torpedoes in the coal piles used to fuel Union steam ships . It was especially intended to be used against ships of the Union blockade , although Courtenay was authorized to act against any Union military or commercial shipping in Confederate waters . Although the Union blockade and other forms of military shipping were Courtenay ' s primary targets , he also had plans to use the coal torpedo to attack steam locomotives , although no confirmed attacks are known to have been made . On 19 March 1864 , a Union gunboat captured a rebel courier crossing the Mississippi , carrying a letter from Courtenay describing the coal torpedo . The correspondence was forwarded to Admiral David Porter , who immediately issued his General Order 184 , which began and vessels in the shape of torpedoes , and an article resembling coal , which is to be placed in our coal piles for the purpose of blowing the vessels up , or injuring them . Officers will have to be careful in overlooking coal barges . Guards will be placed over them at all times , and anyone found attempting to place any of these things amongst the coal will be shot on the spot . In April 1865 , most of the official papers of the Confederate Secret Service were burned by Secretary of State Judah P . Benjamin just before the government evacuated Richmond , making it impossible to determine with any certainty how many ships were destroyed by Courtenay ' s shell . Union Admiral Porter credited the coal torpedo with sinking the " Greyhound " , a private steamboat that had been commandeered by General Benjamin F . Butler for use as a floating headquarters on the James River . Courtenay also took credit for the boiler explosion on the gunboat USS " Chenango " that killed 33 men , though the vessel itself survived and was repaired and returned to duty . In the Spring of 1865 , Canadian customs raided a house in Toronto that had been rented by Jacob Thompson , one of the commissioners of the Confederate Secret Service stationed in Canada . They found coal torpedoes and other incendiary devices hidden under the floorboards . A former Confederate agent named Robert Louden claimed on his deathbed that he had used a coal torpedo to sink the steamboat " Sultana " , killing an estimated 1 , 800 of her 2 , 400 passengers , many of whom were recently freed Union prisoners of war , on April 27 , 1865 , although this claim is controversial . After the Civil War . Courtenay had traveled to England in 1864 and remained there until 1867 , trying to sell the " secret " of the coal torpedo to foreign governments . He approached the British War Office , but they turned him down after he would not agree to allow them to examine his invention before purchasing it . When Courtenay returned to the United States , one or more business partners to whom he had entrusted the secret remained in England . " The Times " in 1873 reported rumors that disreputable ship owners were purchasing coal torpedoes to put in their own ships as a form of insurance fraud , so that over - insured ships and cargo would sink while far out at sea , leaving no evidence . Other reports scoffed at the rumors , suggesting they were false stories planted by supporters of Samuel Plimsoll , a Member of Parliament who was trying to pass a bill reforming the shipping industry . Nothing was ever proven , but the reports stirred up popular interest in various supposed methods of sabotaging ships , and the coal torpedo even made an appearance in the short story , " That Little Square Box , " by Arthur Conan Doyle , published in a story collection entitled " The Captain of the Polestar , and other tales " . Various forms of exploding coal , whether directly descended from Courtenay ' s original idea or independently developed , have surfaced multiple times throughout history . The Fenian Brotherhood , an Irish nationalist organization operating in the United States in the late 1860s – 1870s , reportedly considered placing coal torpedoes in the furnaces of New York City hotels as well as English transatlantic steamships . They were a strong suspect in the destruction of the warship at Punta Arenas in 1881 , but later evidence proved the explosion was accidental . Both the American OSS and the British SOE used forms of exploding coal in World War II . The German commandos who came ashore on Long Island in 1943 as part of Operation Pastorius carried plastic explosives disguised as coal for use against coal - fired electric generating plants . Such a German coal torpedo was given to the British double agent Eddie Chapman ( also known as " Agent Zig - Zag " ) to sabotage the merchant ship " City of Lancaster " , but he passed it on to his MI5 handler instead . Similar devices were also made by the Japanese during World War 2 . Stanley Karnow hints in his book " Vietnam : A History " that the CIA prepared explosive coal for use against North Vietnamese railways during the Vietnam War .