You can read more about it here, but more or less, it's from a book refuting the claims of anti-Nazi cartoonists, which reprints the cartoons.
Such as this dandy little number:
From the link above, a translation of what the book claims:
What they wrote: Simplicissimus (a satirical magazine) suggested in January 1928 that the NSDAP would split so often that in the end only Hitler would be left.Of course, when all is said and done, it's a picture of Hitler hitting himself in the face with an axe. And that is good enough for me.
What happened: The NSDAP did not split, but Hitler was in fact left alone—but in an entirely different sense. Today in Germany there are no parties or party leaders other than Hitler.
Thanks to Olaf, who submitted this is time to make this pretty much the unofficial "Axe Week."