Until they were replaced by the more efficient longbow (Battle of Agincourt, 1415: English: 10, French: 0), crossbows were one of the go-to weapons for armies wishing to inflict damage on each other. Pope Urban II banned its use against ‘other Christians’ in 1096, and Pope Innocent II took the same stand at the Second Council of Lateran in 1139. Using them against non-Christians was apparently okay. Didn’t work, though. People kept using them. Among them, the Papal force of a later Pope, Gregory IV, who felt he had to do something about that dastardly Lombard League.
http://www.historyofarchery.com/archery-history/history-of-crossbows/
https://www.warhistoryonline.com/instant-articles/return-of-soldiers-agincourt.html
Time Travelling With Kids 