The story of the ballista begins in classical Greece around 400 BCE, when engineers turned the handheld gastraphetes and tripod-mounted oxybeles into a beast of war powered by torsion springs. By twisting bundles of sinew or hair into tight skeins, they replaced slow, tension-based bows with levers that snapped back almost instantly, hurling heavy darts or stone balls far beyond what a conventional crossbow could manage. Philip II of Macedon and, more famously, his son Alexander the Great saw the promise in these new engines. Under their armies’ siege towers and on open battlefields, lighter, more portable versions—called scorpions—joined the ranks. Crews could swap from bolt to stone shot on the fly, adjusting to walls, ships or massed infantry without rebuilding their machines from scratch. When Rome absorbed the Greek world in 146 BCE, legionaries adopted and refined the torsion-powered ballista. Wooden frames gave way to metal, winches became standard, and adjustable spring caps let crews tune performance even in rain or heat. By Julius Caesar’s day, ballistae were so trusted that he landed warships on Britain’s beaches just to demo his artillery and kept siege engines trained on Alesia’s walls until Vercingetorix surrendered. In the Empire’s later years, engineers pushed range beyond a thousand meters and mounted ballistae permanently atop London’s city walls. Manuals like De rebus bellicis boasted machines capable of hurling volleys across the Danube. Though the iron-clad corset of Roman rule faded, the ridge of torsion springs and the snap of its levers lived on in medieval torsion catapults and crossbows. By blending Greek ingenuity with Roman precision, the ballista reshaped siegecraft and battlefield tactics for centuries, leaving a legacy both in the ruins of ancient walls and the pages of early military treatises.

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Roman Ballista