The Arsenal

The gladius hispaniensis — 'Spanish sword' — was the primary weapon of the Roman legionary, typically 64–69 cm in length, double-edged, with a point designed for thrusting. Caesar's veterans wielded it with terrifying efficiency: at Pharsalus, Caesar specifically instructed his fourth line to thrust with their javelins at the faces of Pompey's cavalry rather than throwing them, using the weapon's shaft as a spear. The gladius was designed for the press of close-quarters formation fighting, where slashing room was limited but a short thrust under a shield was always available. Roman soldiers trained to step inside an enemy's swinging blow and deliver a 6-inch thrust to the abdomen — a technique requiring discipline and practiced reflexes that Caesar's eight-year Gallic veterans possessed in abundance.

The pilum was a 2-meter javelin with a thin iron shank below the point designed to bend on impact, preventing reuse. A legion typically delivered two pilum volleys at close range (7-8 meters) immediately before charging — the volley disrupted enemy formations, weighed down shields, and eliminated the first rank's ability to fight effectively before the gladius engagement began. Caesar modified the standard pilum design by hardening only the tip and leaving the shank soft, so it bent even more reliably on impact with a shield and was impossible to pull out or throw back. At Pharsalus, Caesar's veterans ignored the pilum order and were told to thrust with them instead — a tactical adjustment specifically targeting Pompey's cavalry that decided the battle.

The scutum was a large curved rectangular shield approximately 1.0 × 0.6 meters, constructed of laminated wood covered in canvas and leather with a central iron boss. It weighed approximately 5.5 kg — heavy enough to require regular shield training to use effectively. In the testudo (tortoise) formation, legionaries locked scuta overhead and on all sides to create an impenetrable shell against projectiles. At siege operations from Brundisium to Dyrrachium, the testudo allowed attacking forces to approach walls and gates under direct missile fire. The scutum's curved inner face braced against the forearm, leaving the sword hand free, and the shield boss itself was used offensively — a punch with the boss could stagger an opponent, opening him for the gladius.

The scorpio was a two-armed torsion bolt-thrower, essentially a large mechanical crossbow mounted on a stand, capable of firing an iron-tipped bolt with enough force to penetrate armor at 200 meters and kill a man at 400. Each Roman legion was equipped with approximately 60 scorpiones, one per century, giving an army of 30,000 men a preliminary bombardment capability of roughly 1,800 weapons. Caesar used them in his fortification lines at Dyrrachium and at the siege of Alesia (Gallic Wars) — they were deployed on towers and ramparts to deny enemy infantry the ability to approach artillery emplacements. The scorpio was accurate enough, in skilled hands, to target specific individuals in an enemy line.

The onager — named for the wild ass, whose kick it resembled — was a single-arm torsion catapult that hurled stones of 15–30 kg in a high arc. Its primary use was siege work: knocking down walls, collapsing gates, and scattering defenders on ramparts. At Alesia (52 BC, Gallic Wars) Caesar deployed dozens to suppress Gallic counterattacks. During the civil wars they appeared at every significant siege — Brundisium, Dyrrachium, Thapsus. The onager's arc-fire capability allowed it to drop projectiles behind walls that direct-fire weapons couldn't reach, and incendiary projectiles — clay pots of burning oil — could fire buildings inside a defended position. Range was approximately 200–400 meters.

The Liburnian — originally a fast pirate vessel from the Adriatic coast — became the standard warship of Agrippa's fleet at Naulochus and Actium. Smaller and faster than the heavy quinqueremes that dominated Antony's fleet, Liburnians could be rowed with two banks of oars and crewed by fewer men, making them easier to fill in Octavian's man-poor western fleet. Agrippa used them in a swarming tactic: multiple Liburnians attacking a single larger vessel from different angles, using the harpax to lock on and board rather than ram. The Liburnian's agility made it effective at avoiding the ram strike that was the heavy quinquereme's primary weapon. After Actium, the Liburnian became the standard Roman patrol and river vessel for centuries.

The quinquereme ('five-oared') was the dominant heavy warship of the Hellenistic Mediterranean — a massive vessel powered by approximately 270 oarsmen arranged in complex banks, displacing perhaps 100 tons and mounting a heavy bronze ram at the waterline. Antony's fleet at Actium included many massive quinqueremes and even larger vessels (hexaremes and octaremes) because Cleopatra's Egyptian fleet operated heavy ships. These vessels were nearly impossible to sink with Agrippa's Liburnians in direct combat — but Agrippa's harpax made direct combat irrelevant. Once the grapnel locked two ships together, the superior training of Octavian's legionary marines destroyed Antony's crews in hand-to-hand fighting. The quinquereme's size became a liability.

Agrippa's harpax was his most consequential invention: a modified ballista (bolt-thrower) that fired a large grappling hook on a long chain at enemy ships, penetrating their timber hulls and allowing Agrippa's own ships to winch the enemy vessel close and board it. The corvus (a boarding ramp used by earlier Roman navies) had been abandoned; the harpax replaced its function while solving its disadvantages. Against Sextus Pompey at Naulochus, where his opponents were superior sailors, the harpax allowed Agrippa's inferior sailors to turn the battle into a land engagement fought on the decks of locked ships — where Rome's legionaries consistently won. At Actium, Antony's larger ships made the harpax even more effective: once locked to a quinquereme that could not escape, an Octavian crew simply boarded and killed.

The hasta — a 2-meter thrusting spear — was the primary weapon of allied infantry, eastern auxiliaries, and some Republican forces fighting for Pompey and later the Liberatores. It was longer than the gladius, giving greater reach in open fighting, but it was at a disadvantage in tight formation combat against trained legionaries with scuta. Pompey's eastern levies at Pharsalus (Thessalian, Greek, and Pontic infantry) carried various spear-type weapons. Their tactical integration with Roman-trained legions was difficult, which contributed to the Republican army's loss of cohesion under pressure at Pharsalus. The hasta was also the weapon of the Praetorian Guard in ceremonial contexts.

The contus was a long two-handed cavalry lance (3.5–4.5 meters) used by heavy cavalry and some auxiliary horsemen. Pompey's cavalry at Pharsalus — which he expected to sweep Caesar's right flank — were probably equipped with a mix of the contus and lighter javelins. Caesar's tactical counter specifically anticipated the cavalry attack: his hidden fourth line was instructed to thrust upward at the faces of the cavalry rather than throwing their weapons, exploiting the cavalry's vulnerability to facial injuries (horses can be ridden one-handed with a face wound; a horseman cannot). The contus cavalry's strength — its charging shock power — was negated by the disciplined infantry reception Caesar had prepared.

Both sides in the civil wars used incendiary artillery — burning pitch-covered bolts, clay pots of oil ignited before firing, and fire arrows — in siege operations and naval warfare. The burning of the harbor at Alexandria during the Alexandrian War reportedly spread to the Great Library, though modern scholarship disputes whether the Library itself was significantly damaged or whether an adjacent book-warehouse burned. Incendiary weapons were used in the naval fighting at Actium: Antony's larger ships, which were harder to board and resist, were particularly vulnerable to being set alight. Octavian's forces reportedly used burning projectiles to force Antony's crews to abandon ship rather than fight.