In Poland every child is taught that a two-finger salute comes from the battle of Olszynka Grochowska.
I cannot speak for every child in Poland, but I can say that also I was taught that by the Drill Sergeant who formally introduced me to military life in the Summer of 1966. A few months later, when I was commissioned as a Second Lieutenant, the first salute I received was from Sergeant Stanisław Kryla, given with two fingers, though he happened to be in U.S. military uniform at the time.
To this day, I consider it one of the greatest honors I've been paid.