One of the major developments in the military sphere during the Late Middle Ages was the increased use of infantry and light cavalry. The English also employed longbowmen, but other countries were unable to create similar forces with the same success. Armour continued to advance, spurred by the increasing power of crossbows, and plate armour was developed to protect soldiers from crossbows as well as the hand-held guns that were developed. Pole arms reached new prominence with the development of the Flemish and Swiss infantry armed with pikes and other long spears.
What influenced the increasing development of armor?
the increasing power of crossbows