In this story, there was no WWII, and instead we were attacked by alien forces who wiped out most of our race.
The British Airborne Forces in WWII first adopted the maroon beret.
I want to digress a moment to note that reports of strange aerial phenomena are not peculiar to the post WWII period.
People still imitate German accents that they hear in WWII films, although modern Germans do not speak like this anymore.
This heavy armament soon became justly feared by enemies on all fronts during WWII.