I believe it was the Zimmerman telegram that pushed the US over the top and entered the war.
I once read something about the German [Kaiser's] Embassy getting anthrax samples from Johns-Hopkins or the like, and the considered using it on the US.
And then there is now ‘ISIS is on its way to conquer America’, screaming by today’s war mongers, ‘we have to do something’. They ‘have killed a captured American newsman with a knife’. So here comes ISIS on camels, discarded American military arms, improvised devices, stolen planes and suicide vests. Sorry mongers, I’m not impressed until they get a bunch of Messerschmitts, Stukas, Rockets, etc. We have nothing to fear except fear itself.