Isn't all war "the continuation of politics by other means"?

I presume what was meant here was that 20th C fascist movements got big by the strategic use of street violence, in a way that the relatively liberal societies they worked within weren't equipped to counter.

Obviously not the first movement to use street violence, but (in my understanding) the scale and discipline with which it was deployed was a new and distinctive feature.

Fascism is used in a civil sense. Military violence during war is in a different category.