Although Robert Fulton never actually built a spar torpedo, on 4 September 1813 he had described to Captain Stephen Decatur a new method of torpedo attack he had devised. Fulton proceeded to draw a diagram showing a boat supporting two torpedoes on long spars which projected below the level of its keel, and which were to be exploded against the underwater hull of an enemy ship. Since he had acted in an advisory capacity during the war with Britain, it is conceivable that his ideas had been put into practice by others. It is on record, for instance, that HMS Ramillies captured and sank a spar torpedo boat off Long Island in 1813, and there is evidence of their use on the Great Lakes.

The first effective spar torpedo attack had to wait another fifty years, when Confederate Lieutenant William T Glassell, commanding a ‘David’ semi-submersible torpedo boat, exploded his spar torpedo against the Union frigate USS New Ironsides on 5 October 1863. His victim did not sink, but was badly damaged.

The first successful submarine attack was the H L Hunley’s sinking of the USS Housatonic on the night of 17 February 1864, again using a spar torpedo. The little submersible was a desperate measure by the Confederates to break the stranglehold of the Union navy’s blockade of the port of Charleston. Prior to her successful action, she had already drowned most of the men of two of her crews, and following the attack she disappeared. Her wreck was discovered buried in silt and sand not far off Charleston Harbour in 2000. The Friends of the Hunley, the association which raised and is working to preserve her, has full details of this pioneer vessel on their website

Historians had always assumed that the Hunley’s commander would attempt to ram the spar torpedo into the hull of his target like one of Fulton’s harpoons, then withdraw, leaving the weapon impaled in the victim. The charge would be detonated at a safe distance by pulling on a cord attached to the torpedo. Study of the tip of Hunley’s spar, however, has revealed the remains of the copper casing of the torpedo, meaning that it was detonated when still attached to the spar. A Singer drawing of the torpedo in The National Archives has been used to calculate that it contained a charge of up to 135lbs (61kg) of black powder. As the spar is only 16ft (4.9m) long, detonating this large charge at such a short distance could well have knocked several crew members unconscious. We know the Hunley survived the explosion, since the commander of Fort Moultrie saw the prearranged blue magnesium light signal to indicate the mission had succeeded, a blue light also seen by survivors of the Housatonic. She may have been damaged by the blast in such close proximity, but the fact that her wreck was eventually discovered not far off Charleston Harbour and safety, has forced historians to revise their notions that the spar torpedo was basically a suicide weapon, as dangerous to the assailant as the victim.

Spar torpedoes were fitted to other Confederate vessels, in particular the ironclad CSS Richmond, which carried a spar torpedo projecting from her bow underwater. When taken up by the Union side, a significant change was made. Whereas the Hunley, in order to approach her target unseen until the very last moment, had been designed as a submersible, and was therefore vulnerable to even a small amount of damage caused by the underwater shockwave, the Union spar torpedo crews used surface boats to bring their torpedo into contact with the underwater part of the enemy’s hull, just as Fulton had intended. If their boats were sturdy enough, they would have their bows lifted by the underwater explosion but with luck they would survive. The enemy vessel, holed below the waterline by even the modest charges of the day, and with no internal subdivision, would head for the bottom.

The Union’s spar torpedo boats claimed their first victim under the command of the young daredevil Lieutenant William Barker Cushing. At the age of three he had run away to sea, falling off the end of a jetty while pursuing a departing ship. Saved from drowning by a nearby sailor, he had decided a year later to depart to see the world on one of his father’s horses. Attempting to shoe it himself, the four-year-old had been kicked senseless by the indignant horse. Dropped from the naval academy because of endless pranks, he answered his nation’s call when civil war broke out, and managed to have himself reinstated into the navy. The attack on the troublesome rebel ironclad Albemarle was Cushing’s idea. With the help of John Lay, he rigged up two steam launches as spar torpedo boats and set off for the Albemarle’s lair on the Roanoke River. One launch sank en route, but on the night of 27 October 1864 the attack went in. Finding his prey protected by a boom of floating logs, Cushing circled some way off, then called for full steam to enable his launch to leap the slime-covered log boom. Having crossed this barrier, he manipulated Lay’s four lanyards, one attached to each of his hands and feet, to deploy the torpedo head underneath the hull of Albemarle and then detonate it. The explosion swamped his launch, forcing Cushing and his crew to abandon it and try to escape as best they could. The Albemarle, despite the efforts of her commander, Lieutenant Warley and his crew, sank to the river bottom with a hole blown in her bows. Cushing was eight days short of his twenty-second birthday.

The relative effectiveness of the spar torpedo led all other naval powers to adopt it in one form or another. Following the end of the American Civil War, the next use of the spar torpedo in anger was by the Russians on the Danube and in the Black Sea during the Russo-Turkish war of 1877–78, and then by the French against the Chinese seven years later (for details see Part IV).

Inspired, no doubt, by their countrymen’s pioneering use of the spar torpedo, and bolstered by Russian and French successes in the years since the end of the civil war, the Torpedo Station was still issuing detailed Spar-Torpedo Instructions for the United States Navy as late as 1890. According to these instructions the standard outfit of Service spar torpedoes comprised a set of twenty-four, with twelve for use on board ship and twelve for the ship’s boats.

Each Service spar torpedo measured 12in (30.5cm) long by 9in (22.9cm) square, all inside measurements. They were fabricated from sheet iron tinned inside and out, the inside surfaces being shellacked and the exterior asphalted. The empty case weighed about 15lbs (6.8kg), and the charge was equivalent to 34lbs (15.4kg) of dry gun-cotton, including the primer. The latter was fired by electricity, rubber grommets being arranged in the top of the case. Exercise torpedoes were also available, slightly longer than the Service type but only a third of the width and depth, and shellacked inside and outside. The Exercise torpedo weighed 3lbs (1.4kg) and its charge of dry gun-cotton added another 4lbs (1.8kg). The firing circuit was to be made up by cutting and connecting suitable lengths of insulated double cable from the 300ft-long (91.4m) reel supplied.

The Service spar torpedo for boat use would be attached to a spar made up of two steel tubes 18ft and 15ft long which telescoped one inside the other with an overlap of 2ft (9.45m total length), held in place in the bow of the boat by a complex system of yokes and gearing, to permit accurate placing of the torpedo. The boat torpedo was to be immersed to a depth of at least 10ft, and could safely be exploded 22ft away horizontally (3m deep by 6.7m distant).

Interestingly, the Service spar torpedoes for ship’s use were to be attached to the ends of 45ft-long (13.7m) wooden spars braced out from the sides of the ship, one on either side of the foremast and one on either side of the mizzen. Ship’s torpedoes were also to be immersed to a depth of at least 10ft, but to ensure the safety of the attacking ship had to be exploded at a distance of at least 35ft (10.7m) from her hull. For the Exercise torpedo, an immersion of 5ft at a range of 20ft was suitable for firing from both a boat and the ship (1.5m depth at 6.1m distance). Instructions were also provided for converting the Service torpedo to a contact exploder, and for constructing improvised spar torpedoes from wooden kegs or casks, caulked on the outside to make them watertight, and charged with black powder.

For its part, the Royal Navy also continued with the spar torpedo up to and beyond the end of the nineteenth century. One design comprised a metal cage enclosing a ring of six TNT cylinders placed around a seventh cylinder, to which was attached an electrical primer and lead to a battery on the launch. Firing was initiated by a pair of contact horns protruding from the head of the torpedo.

The surviving early film sequence shot by Alfred West in around 1898 shows Royal Navy spar torpedo exercises, probably in Fraser Lake, which was part of Portsmouth Harbour. In the full sequence, when the huge water plume has subsided, the steam pinnace setting off the spar torpedo explosion appears unharmed.