Grapnels such as this, attached to lengths of rope, were thrown to ensnare an enemy ship and to pull it close enough to enable it to be boarded. A variation of this was attached to a shaft (the harpax) which could be shot from an artillery piece for longer range. Iron grapnel, second century AD.
Before the Punic Wars Roman naval activity had for the most part been carried out by a modest numbers of smaller ships, against like opponents and boarding an enemy vessel had been an ad hoc affair. In the great wars, large numbers of big ships carrying tens of thousands of men were engaged and pitted against an enemy, initially superior in seamanship to the majority of the Roman ships. Additionally, far larger contingents of marines were carried who, to be effective, had to have some means of crossing to an enemy deck, while themselves being under attack.
If ships lay close alongside each other, marines were able to clamber across the gap along the ship’s length. The Carthaginians preferred ramming attacks and so the gap across their bows was too great to jump. The Roman solution was to mount a ‘bridge’ 36 feet long (11 m) and 4 feet wide (1.2 m) with a slot in one end which fitted around a post 24 feet in height (7.3 m) mounted in the foredeck; the bridge was hauled up by rope and pulley, to be held almost vertically against the post. At the other, free end of the bridge was a metal spike (the actual corvus, raven’s beak) the slot allowed the bridge to be adjusted as to length and swung from side to side, so that when the Roman ship came within range, the bridge was dropped across the enemy deck, into which the corvus embedded itself, locking the ships together. The bridge was wide enough for men to cross two abreast and, covered by missiles shot from their towers, the Roman marines could swarm across. The bridge had a low rail on each side to knee-height and the soldier’s shields covered them from knee to shoulder, so is was preferable to pass starboard to starboard of the enemy and drop the corvus so the marines would cross with their shielded sides to the enemy. The equipment was bulky and could only be mounted on the big quinqueremes.
Although outstandingly successful in action, the drawback was that the corvus was heavy and mounted high in the very bows, it added considerable top weight and adversely affected sea-keeping qualities. The loss of so many ships equipped with it in storms led to the device being discarded by about 250 BC and being replaced by an alternative form of ‘boarding bridge’. No description of this device survives but it was lighter and able to be dismantled and stowed on deck, or even jettisoned if necessary, in effect a lightweight corvus, able to be manhandled without the need for the heavy post and tackle.
Artillery was a feature of ancient warships almost from its invention in the early fourth century BC. At that time the engineers of Dionysius, the tyrant of Syracuse, made a large composite bow, larger and more powerful than could be drawn by a man, this they mounted on a timber stock, together with a winch and trigger mechanism to draw and release it. The whole was connected to a stand by a universal joint which enabled the machine to be trained both vertically and horizontally and thereby aimed. The stock to which the bow was fixed had a central channel along the top in which was fitted a slider with the trigger mechanism and a channel for the missile; this was locked to the bowstring and the whole slider pulled back by the winch, checked by a ratchet along the sides of the stock. Upon release of the missile, the slider was pushed forward, to re-engage the bow string and winched back again to reload. These machines could hurl a large arrow or, with an adaptor, a stone shot, up to 300 yards (275 m). Mounted on ships, they could cause devastation if shot among an enemy’s rowers, easily piercing the leather screens which had been sufficient to stop javelins or arrows and which had provided their protection up to then; the advent of artillery led to the progressive boxing in of the rowers, to provide them with sufficient armour protection.
Reliable and simple to maintain, these machines were in use until about 240 BC; before that, the engineers of Philip II of Macedon (reigned 359–336 BC) had perfected a new type of propulsion system for artillery. The composite bow was replaced by two short bow staves, each inserted into a skein of animal sinew which had been woven into cords, stretched, oiled and twisted to form torsion springs which stored great power. These were mounted in special carriers and kept in tension by passing them through a hole and washer at the top and bottom and retained by a bar; they were mounted each side of a stock with slider and trigger, similar to their predecessors. Being a good deal more powerful, range was increased to some 400 yards (366 m) and they could be made in ever increasing sizes. The springs were susceptible to damp and needed to be regularly removed and restretched and oiled, requiring in turn, specialised artillery artificers. As the pieces were made by estimating, with no set pattern of parts, performance could vary greatly, which is why the earlier form continued in use.
From about 275 BC Ptolemy of Egypt’s engineers had developed a formula for building torsion spring artillery pieces. Starting with the length of arrow that the intended machine was to shoot, the formula dictated the fraction of that length (it was 1/9th) which was to be the diameter of the holes in the carrier through which the springs would pass. All dimensions of all of the components of the machine were then dictated by the formula, as multiples or fractions of that hole diameter. These ‘formula machines’ proved to be reliable, of known performance and could be mass produced in standard sizes.
These machines supplanted the earlier types and became standard equipment aboard warships. The smallest type seen to mount artillery was the trireme, whereas quinqueremes and larger types could carry up to ten. The larger ships could also carry larger sizes of catapult. These weapons, although capable of inflicting damage to crew and ship, were not ‘ship destroyers’, and the modestly sized and well attested three-span (shooting an arrow 27 inches in length (685 mm) with a stock length of 4 feet 6 inches (1.27 m) and two-cubit (3-foot or 915 mm arrow) with a stock length of 6 feet (1.83 m) machines would have been ideal as anti-personnel weapons.
Apart from shooting at each other, warships could bring their artillery to bear in support of an opposed troop landing, as Caesar’s ships did in Britain in 55 BC and again in his attack on the Heptastadion at Alexandria in 47 BC. Artillery on ships could also be used as floating batteries, as was done to cover the building of a bridge over the Euphrates in AD 62.
Apart from the normal complement of arrow and stone shooters, larger machines were on occasion, mounted for siege or assault work, especially during the Punic Wars. Siege artillery was substantially larger and predominantly stone throwers, the very biggest being capable of hurling a stone shot weighing an amazing 260 pounds (118 kg). Although siege machines smaller than this were mounted, the additional weight of the machine and of its stone shot had to be considered. The weight of a three-span piece has been estimated at about a hundredweight (112 lb, 61.7 kg) and that a quinquereme could carry ten, plus a couple of small stone throwers and still have its normal complement of forty marines. Clearly the installation of such machines had to be offset by weight savings, the marines being replaced by artillerymen and the rowing crew being reduced to just enough to manoeuvre the ship into position and all stores landed.
As examples of this practice, in 210 BC, the Roman fleet supported an assault upon Naupactus from seaward using siege artillery. A year later, in 209 BC, both war- and merchant ships were so equipped for the siege of Taranto and warships with extra artillery joined the assault on Cartagena. Finally, Scipio put siege artillery aboard his warships for a feint against Utica in 204 BC.
Grapnels attached to a line and thrown, had long been in use to ensnare and pull an enemy ship in so that it could be boarded but for the war against Sextus (38–36 BC) Octavian’s admiral Agrippa introduced the harpax (harpoon), a grapnel attached to the end of a shaft 7.5 feet in length (2.3 m.) and lined with metal strips so that it could not easily be cut through. It was shot from the larger onboard catapults and trailed a line which could be hauled in. Although the range of the machine was considerably reduced by the added weight of the missile and the drag of the line, it could still far outrange any hand-thrown grapnel.
Artillery was not mounted on towers which, being comparatively flimsy, could not support the weight or the shock of discharge of the machines. Further, the position of the universal joint mounting, close behind the spring-carrier frame, prevented the piece from being depressed to shoot down on to an enemy deck. Low platforms for artillery were sometimes erected on deck to give an elevated position and enable them to shoot on either beam.
In the late first century AD there was a radical redesign of the smaller types of artillery pieces which resulted in replacing the former wood and iron spring assemblies with finely made all-metal parts for the torsion spring carriers and their mounting frame. Although more complex and requiring more specialised manufacture, they could be dismantled and worn or damaged parts quickly replaced, the parts being standardised and interchangeable. They were more compact and also more powerful, range being increased to in excess of 500 yards (457 m). These are the machines so much in evidence on Trajan’s Column. Light, compact and powerful, these machines were ideal for mounting on warships, including many of those too small to have carried the earlier types.