What are some early examples of an air force facing hostile a/c
originally produced by its own country's aviation industry (whether they
were sold to a former friendly nation that then became an enemy, or were
captured a/c, or whatever)? The first case I can remember reading about
is during the Allied invasion of N. Africa, when P-36s flown by Vichy
French were encountered, but it seems there must have been previous
instances -- WWI, interwar, or earlier WWII.