Catapult A catapult is a device used to throw or hurl a projectile a great distance without the aid of explosive devices — particularly various types of ancient and medieval siege engine s . Although the catapult has been used since ancient times , it has proven to be one of the most effective mechanisms during warfare . The word ' catapult ' comes from the Latin ' catapulta ' , which in turn comes from the Greek καταπέλτης ( " katapeltēs " ) , itself from ( " kata " ) , " downwards " + πάλλω ( " pallō " ) , " to toss , to hurl " . Catapults were invented by the ancient Greeks . Greek and Roman catapults . Catapult and the crossbow in Greece are closely intertwined . Primitive catapults were essentially “ the product of relatively straightforward attempts to increase the range and penetrating power of missiles by strengthening the bow which propelled them ” . The historian Diodorus Siculus ( fl . 1st century BC ) , described the invention of a mechanical arrow - firing catapult ( " katapeltikon " ) by a Greek task force in 399 BC . The weapon was soon after employed against Motya ( 397 BC ) , a key Carthaginian stronghold in Sicily . Diodorus is assumed to have drawn his description from the highly rated history of Philistus , a contemporary of the events then . The introduction of crossbows however , can be dated further back : According to the inventor Hero of Alexandria ( fl . 1st century AD ) , who referred to the now lost works of the 3rd - century BC engineer Ctesibius , this weapon was inspired by an earlier foot - held crossbow , called the " gastraphetes " , which could store more energy than the Greek bows . A detailed description of the " gastraphetes " , or the “ belly - bow ” , along with a watercolor drawing , is found in Heron ' s technical treatise " Belopoeica " . A third Greek author , Biton ( fl . 2nd century BC ) , whose reliability has been positively reevaluated by recent scholarship , described two advanced forms of the " gastraphetes " , which he credits to Zopyros , an engineer from southern Italy . Zopyrus has been plausibly equated with a Pythagorean of that name who seems to have flourished in the late 5th century BC . He probably designed his bow - machines on the occasion of the sieges of Cumae and Milet between 421 BC and 401 BC . The bows of these machines already featured a winched pull back system and could apparently throw two missiles at once . Philo of Byzantium provides probably the most detailed account on the establishment of a theory of belopoietics ( “ belos ” = projectile ; “ poietike ” = ( art ) of making ) circa 200 BC . The central principle to this theory was that “ all parts of a catapult , including the weight or length of the projectile , were proportional to the size of the torsion springs ” . This kind of innovation is indicative of the increasing rate at which geometry and physics were being assimilated into military enterprises . From the mid - 4th century BC onwards , evidence of the Greek use of arrow - shooting machines becomes more dense and varied : Arrow firing machines ( " katapaltai " ) are briefly mentioned by Aeneas Tacticus in his treatise on siegecraft written around 350 BC . An extant inscription from the Athenian arsenal , dated between 338 and 326 BC , lists a number of stored catapults with shooting bolts of varying size and springs of sinews . The later entry is particularly noteworthy as it constitutes the first clear evidence for the switch to torsion catapults which are more powerful than the flexible crossbows and came to dominate Greek and Roman artillery design thereafter . This move to torsion springs was likely spurred by the engineers of Philip II of Macedonia . Another Athenian inventory from 330 - 329 BC includes catapult bolts with heads and flights . As the use of catapults became more commonplace , so did the training required to operate them . Many Greek children were instructed in catapult usage , as evidenced by “ a 3rd Century B . C . inscription from the island of Ceos in the Cyclades [ regulating ] catapult shooting competitions for the young ” . Arrow firing machines in action are reported from Philip II ' s siege of Perinth ( Thrace ) in 340 BC . At the same time , Greek fortifications began to feature high towers with shuttered windows in the top , which could have been used to house anti - personnel arrow shooters , as in Aigosthena . Projectiles included both arrows and ( later ) stones that were sometimes lit on fire . Onomarchus of Phocis first used catapults on the battlefield against Philip II of Macedon . Philip ' s son , Alexander the Great , was the next commander in recorded history to make such use of catapults on the battlefield as well as to use them during sieges . The Romans started to use catapults as arms for their wars against Syracuse , Macedon , Sparta and Aetolia ( 3rd and 2nd centuries BC ) . The Roman machine known as an arcuballista was similar to a large crossbow . Later the Romans used ballista catapults on their warships . Medieval catapults . Castle s and fortified walled cities were common during this period - and catapults were used as a key siege weapon against them . As well as attempting to breach the walls , incendiary missiles could be thrown inside — or early biological warfare attempted with diseased carcasses or putrid garbage catapulted over the walls . Defensive techniques in the Middle Ages progressed to a point that rendered catapults ineffective for the most part . The Viking siege of Paris ( 885 – 6 A . D . ) “ saw the employment by both sides of virtually every instrument of siege craft known to the classical world , including a variety of catapults , ” to little effect , resulting in failure . The most widely used catapults throughout the Middle Ages were as follows : Modern use . The last large scale military use of catapults was during the trench warfare of World War I . During the early stages of the war , catapults were used to throw hand grenade s across no man ' s land into enemy trenches . ( These were eventually replaced by small mortars ) . Special variants called aircraft catapult s are used to launch planes from land bases and sea carriers when the takeoff runway is too short for a powered takeoff or simply impractical to extend . Ships also use them to launch torpedoes and deploy bombs against submarines . Small catapults , referred to as " traps " , are still widely used to launch clay target s into the air in the sport of clay pigeon shooting . Until recently , catapults were used by thrill - seekers to experience being catapulted through the air . The practice has been discontinued due to fatalities , when the participants failed to land onto the safety net . Pumpkin chunking is another widely popularized use , in which people compete to see who can launch a pumpkin the farthest by mechanical means ( although the world record is held by a pneumatic air cannon ) . In January 2011 , popsci . com , the news blog version of Popular Science magazine reported a group of smugglers used a homemade catapult to deliver marijuana into the United States from Mexico . The machine was found 20 feet from the border fence with bales of marijuana ready to launch . Models . In the US , catapults of all types and sizes are being built for school science and history fairs , competitions or as a hobby . Catapult projects can inspire students to study different subjects including physics , engineering , science , math and history . These kits can be purchased from Renaissance Fairs , or from several online stores .