Episode 3 tracks the development of artillery from the ancient Greeks, through the invention of gunpowder in China, to the very latest generation of big guns and directed-energy weapons. Throughout the ages, the ability to strike from a distance has been critical to success in battle, and time and again, artillery weapons have forced armies to adjust to ever-more powerful technology. Starting with the Greek gastrophetes—a tension-powered mechanical bow—artillery evolved into the torsion-powered Roman ballista, and then the massive counterweight trebuchet, which was used to toss everything from rocks and fireballs to severed heads and whole people. But once again, it was the arrival of gunpowder that truly transformed artillery warfare. The marriage of gunpowder and barrel sparked a revolution in every aspect of firearms design. From bamboo, iron, bronze and then steel barrels, to changes in the formulation of the gunpowder itself, to elongated, spinning projectiles, to advanced recoil mechanisms and special tools and calculations for aiming, every generation built on the previous to create ever-more-accurate, far-reaching and deadly big guns.