[Major]

Originally Posted by Espy

What country was responsible for the creation of the dreaded Red Devils?

Red Devil, singular, is Richthofen, but we’re talking plural, so...

...Japan...? Squadron of soldiers who wore armor that was painted red to scare the enemy?

Are you sure you're not thinking of Manfred von Richthofen, the Red Baron? Unfortunately, I couldn't find the meaning of the name Richthofen, but "red devil" in German is roter Teufel (singular).