This common weapon was so ‘pernicious’ that Catholicism banned it
In 1096, Pope Urban II took a good hard look at this new "crossbow" thing and gave it all of the nopes. No Christians were to use it in any battle against a fellow Christian on the punishment of excommunication and eternal damnation of the soul. But the weapon that would act as the precursor to the rifle was simply too valuable to leave on a shelf.
A figure depicting a crossbowman who helped execute Saint Sebastian in the later 15th Century.
(Gun Powder Ma, CC BY-SA 3.0)
Crossbows were already an old weapon when European knights first ran into them in the 900s. Ancient Europeans had used similar weapons, but crossbow-like designs had fallen out of favor in Europe by the year 500 A.D., and few Europeans would've recognized them before their resurgence in the late 900s and 1000s.
But French use, as well as use by Eastern nations who had never stopped using the weapon, brought it back into the lexicon of European warfare.
And Western knights did not like it. Their armor protected them from most weapons they would face with the exception of the longbow, a weapon that took years to learn and decades to master. But crossbows could slice right through the armor at greater range than even a longbow, and shooters could be trained in hours or days.
The French were the ones who brought the crossbow back into European warfare. The English had a huge advantage when it came to bowmen, especially longbowmen, and France and England fought often. But while crossbow shooters could fire at greater ranges and with less training than soldiers equipped with a longbow, the weapon did have disadvantages.
Crossbows fire only two rounds per minute while good archers with longbows could fire 10. And crossbow units needed supporting staff and spare parts that weren't necessary with traditional archers. They were also more susceptible to weather damage because it was harder to remove and replace their sensitive strings.
Still, the advantages outweighed the problems, and units across Europe adopted the new weapon. Mercenary units recruited and trained skilled crossbowmen and sold their services. For a few years, kings largely tried to follow the ban on using crossbows against Christian foes, and Pope Innocent II continued the ban in 1139 after ascending to the position of Pope.
Saint Sebastian was martyred by archers, reportedly at least one of which was using a crossbow.
(Hans Baldung, public domain)
But it couldn't last. Kings used the weapons against pagans and Muslims, but then had to leave the men behind while fighting against each other in Europe. By the early 1200s, they were once again common in European combat. Crossbowmen played a crucial role for Holy Roman Emperor Frederick II in 1238.
In fact, just a year later, Pope Gregory IV used mounted crossbowmen against the Lombard League, an alliance of European kingdoms that were all Christian. Yeah, the allure of crossbow power was so strong that a pope employed them against Christian forces.
Crossbows would continue to play a role in combat until after the 15th Century when advances in gunpowder slowly rendered them obsolete. First, advanced cannons were able to break up their formations from further away than even the crossbowmen could fire. And muskets and rifles eventually filled the role that crossbowmen once had.
Of course, the church didn't love firearms either. It declared all black powder weapons to be daemonic, but armies quickly embraced them anyway.