Prove that the use of firearms changed military affairs in Europe.

We are talking about the events of the XIV-XVI centuries, that is, the late period of the Middle Ages and the beginning of the New Age. The massive use of firearms led to the decline of feudalism, as the castles of the feudal lords were vulnerable to artillery. The first use of cannons dates back to the battles of the Hundred Years War, around 1370.
With the advent of firearms, mass infantry with arquebusses and muskets appeared, which could repel the attack of the few but expensive units of knights.