I spent a lot of time fighting imaginary Germans as a kid... but we also defended ourselves against:
Klingons, Stormtroopers, Red Coats (what you didn't have a toy musket?), The Spanish (when playing pirates.. another use for a musket and toy cutlass), invaders from mars, Communists, Apes (as in Planet Of The Apes: the TV Series), The Japanese, Dinosaurs and super villans.
I had a J7 (or something VERY like it) as a kid... very useful in most of the above scenarios.