Medieval War machine The counterweight trebuchet appeared in both Christian and Muslim lands around the Mediterranean in the twelfth century. It could fling projectiles of up to three hundred and fifty pounds (140 kg) at high speeds into enemy fortifications. Occasionally, disease-infected corpses were flung into cities in an attempt to infect and terrorize the people under siege, a medieval form of biological warfare.The trebuchet did not become obsolete until the 13th century, well after the introduction of gunpowder. Trebuchets were far more accurate than other medieval catapults