I've been thinking about some of the ways things change, and the things that drive the changes.
Right at the moment, firearms are in mind. Lots of people get hung up on the 'guns are bad' idea and either cannot or won't see it any other way.
Once, armies were a core of nobles and attendants, supported by lots of peasants and slaves. When going to war they often took a lot of peasant levies along, but they were mostly for work parties and to get in the way of the enemy.
Then the gun arrived.
When they stopped being clumsy, unreliable toys, they became essential. First cannon, then individual arms. And they changed armies, and the society they were supported by/created by. It takes years to learn to use a sword and shield well; add in a horse and lance, longer, it's best to grow up learning it(nobles). The bow is the same, years of practice to become skilled enough to be useful. And able to handle a bow strong enough to be really useful in a fight. Think Welsh, and Mongol, growing up with stronger bows every year. /side note: it would be interesting to find out how many people wound up with repetitive-stress injuries; sword and bow and axe practice means a lot of the same motions/
But you can train someone to the point of useful skill with a musket in a few weeks. You don't need untrained peasants to wave sticks now, you need people who can take and follow orders and train to be steady under fire. Long term, that means more than changes in an army, it means changes in the society as well.
A gun means you don't have to be big and strong, or spend at least an hour a day practicing, to be able to protect yourself. Yes, bad guys used guns; they've always used the weapons available. Now you had a weapon that made you able to fight a big bad guy even if you were small. /side note: I don't care what people say about empty-hand martial arts, and stun guns, and batons; anyone who lets a bad guy get within reach, if you don't have to, is a fool. The idea is to protect yourself; leave ideas like 'honorable combat' where they belong, which is not in your head when someone attacks you in your home, or a parking lot, or wherever/
Much has been made of the Japanese being the people 'who gave up the gun' because it didn't suit their warrior ethic. Horsecrap. The Samurai used guns, and very effectively, when it suited them. Where the gun did not suit them was in the hands of peasants; it's hard to be a noble samurai, lopping the heads off insolent peasants, if the peasant can shoot you before you're in reach of your sword. They had already banned peasants having weapons of war, firearms were just included in the ban.
Especially as guns became more generally useful, you could tell more about the relative freedom, and respect for the individual, in a society by the attitude toward them. Many places, only military/police/nobles were allowed them most of the time(peasants; Britain, in contrast, pretty much integrated them as more of the arms a subject was supposed to have/know how to use in time of need (yes, I know they did have some restrictions, especially as to religeon of owners; it was still generally expected that a loyal subject of the crown had the right to arms and self-defense. It wasn't until the 1900's that British law began restricting the ownership of arms from honest subjects)
For a lot of people who emigrated to North America, it was a given that you would possess arms, and practice with them. It was considered important enough that when the 2nd Amendment was first proposed, most states though it unnecessary; the right of free men to arms seemed so basic to them that they thought it didn't even need to be mentioned. A couple of states insisted they would not ratify the Constitution unless it was, and so- thank you, founders- we have the 2nd Amendment. Otherwise we might well have gone the way of Britain and Canada and Australia.
This is a short & dirty bit of thought on the matter, but I think it holds true.
I may add to it later.