I’m about halfway through a very good book called “A Rifleman Went To War” by McBride. It’s his account of WWI trench warfare. (Briefly, he was an American that went to the Canadian army to get to combat faster… he was a Machine Gunner/Sniper)
He notes that the Canadian army captured a German who had a “pen light” attached to his rifle. He thought it was the darnedest thing.
So, as far as I have read, that’s the earliest use of a light attached to a rifle. Obviously technology and battery usage/life dictated when the earliest time a flashlight could be used on a rifle, but I don’t want to hear guys saying that putting a light on their AR or other carbine is some kind of newfangled thing. It was tried out almost 100 years ago.
Excellent book so far by the way. McBride’s personality reminds me a lot of Coughlin’s (the guy who wrote the book “Shooter” - not the one that was made into a movie, the one about the USMC sniper…).