The weapons used during the Middle Ages included the Crossbow. The correct term for a crossbow is an Arbalest. The crossbow applied engineering to the short bow. The crossbow bolt, unlike a light flying arrow, was short with a deadly point. The crossbow range was 350 – 400 yards but could only be shot at a rate of 2 bolts per minute. The crossbow was easy to use, requiring minimal training and required little strength to operate.
One of the main differences in the crossbow, or as the Romans called it the arcuballista or arbalest, compared to the longbow is the force it uses for throwing its bolt. The bow that Englishmen are famous for shoots it's arrow with 60 to 180 foot pounds of force or lb. The crossbow used against knights for its armor penetration could reach forces of 350 lb. Another major difference was the ease of use of the crossbow over any other weapon of medieval times. The crossbow was easily aimed and a peasant could be taught its use in a week. Compare this to the years of training those Englishmen would require to become the feared longbow men.
Armor penetration was the major result of this more forcefully thrown bolt. Thicker armor would better protect the wearer from crossbow bolts but not against some of the later heavier versions. The crossbow bolts could penetrate mail and lighter plate armor as well as the kinks or spots between that armor used for movement at joints. Plate mail or a thick breast plate would stop most crossbow bolts but the bearer of the crossbow could easily aim a shot at those vulnerable spots much more easily than a longbow man. To have the crossbow cocked and ready to be fired by pulling the trigger meant you could hold the weapon at the ready and wait for a good shot without tiring the user. This resulted in better placed shots compared to your average longbow shots, and a weapon that was effective against a heavily armored man such as the heavy infantry.
The earliest reference to crossbow use was in the Battle of Ma-Ling, in Lingyi, China in 341 BC. It was widely used in China for hundreds of years after that, being a primary weapon in battle. Many Chinese Emperors were found surrounded by soldiers armed with crossbows.
The Chinese made several advances and upgrades to the classic crossbow, including the repeating crossbow. This advanced weapon was used until 1895 by troops in the China-Japan war.
The Romans also 'invented' crossbows, but were very rough in design as compared to their Chinese counterparts.
Until the mid-1400's, the crossbow's prod was made of wood. This made the crossbow much lighter, and easier to carry. It was also easier to span and much quicker to fire. Composite prods (made of several materials, including horn) were much heavier. Composite prods had much harder draw forces, which is the string tension. In some cases, the soldier needed a winch to draw the string, as it was nearly impossible to do by hand. Composite crossbows also took a very long time to make, and for the glue to dry, and as a result many of them would be drying out for more than 6 months.
In the late 1400's, steel was used more frequently in the production of crossbows. Steel brought more durability, and strength to the prod and the crossbow as a whole. It was also about this time that the use of the crossbow changed as well. Soldiers started placing the butt of the stock on their shoulder to steady them, and to improve accuracy.