Long guns have been in the hands of soldiers for centuries. There are even medieval illustrations of European armored knights with “hand gonnes” dating from the 14th Century — proof that people have been using metal tubes loaded with gunpowder to shoot projectiles for quite some time.
The rifle is quite another matter. Despite the fact it is far more accurate than the smooth-bore muskets that dominated European warfare for 300 years, it is a relative newcomer to the battlefield.
But it was the Baker Rifle that convinced many generals that the rifle should be an infantryman’s weapon, not just the firearm of specialists. My article at War Is Boring tells the story of the Baker Rifle and how it transformed the ordinary soldier into a long-distance killer. The battlefield was never the same afterward.