Just prior to the start of WWII, Nazi Germany managed to use lots of induced street violence and fake stories about German unification supporters being suppressed to take over Austria without themselves firing a shot, and then used fake stories about ethnic Germans being oppressed and abused to do the same thing with the defensible western portion of democratic Czechoslovakia. They were in the process of pulling the same maneuver with Poland (they even had a secret partition agreement worked up with the USSR) when France and England drew the line. At that point it was arguably too late to stop them.

Its not like Hitler invented political subversion propaganda though. This is a time-honored technique of attacking another country indirectly, particularly useful when softening it up for invasion. Democracies are particularly vulnerable to it due to the fact that they must allow dissenting political speech in order to function properly.