Crossbows were already known in ancient China but, apparently, were invented again in Europe around the 5th century BC. They had good range and were more powerful that most of the bows, although it took much longer for them to load. A crossbowman could shoot an average of two arrows per minute.
Crossbow bow is held horizontally and fired by a trigger that released the taut rope. To load it, a soldier would hold the front of the weapon to the ground, holding it with your foot. He then could pull the rope up and back with both hands or with the help of a crank. Crossbows fired bolts or linear arrows, which were much shorter than the typical arrows. The arrows had feathers to provide stability in flight and a sharp metal tip.
The archers used to carry a few large shields to protect themselves while they crouched to reload their weapons. Thus they formed a wall that protected them. When they were shooting, were only visible their crossbows and their heads with helmets. If they had to fight a similar force of long-range archers, usually they were forced to retreat.
The crossbow was a deadly and very popular weapon for the simple reason that almost no training needed to handle it. Soldiers with little experience could learn its management very quickly, and a well-aimed shot could kill a gentleman who had spent entire life training in the arts of war. Crossbows were considered unfair in some circles (in the Knights, mainly) because a little skill required. Richard I of England, Lionheart, was wounded twice by crossbow, the second with fatal consequences. The idea that a man of his greatness was mortally wounded as easily by a common soldier, was unbearable for the nobility. In the 12th century, a Pope tried to prohibit the use of crossbows as inhumane.