How long would it have taken for new weapons, armor, and strategies to become universal?

by sonofdurinwastaken

For example; when the bow and arrow first showed up in war, how long before it was being used by all armies?

voyeur324

/u/Pachacamac /u/retarredroof and /u/Reedstilt have answers to questions like yours in the subreddit FAQ, mostly focused on the Americas.

EDIT:

See also the general "weapons development" section of the FAQ for more.