If you happen to indulge in reading about WW II and the many 'war-tools' that was introduced by Japan & Germany, this article maybe of interest to you.
Along about September of 1943 the Allies couldn't quite wrap their minds around "why" there was a sudden rise in warship losses
Well there was a new "tool" that the enemy was not putting on the neon war billboard.
They (the enemy) was saying silently to whomever....we are introducing you to
If you care to give this a going over, I think you'll find it most interesting.