The Social Democrats, the largest party in the German national legislature, were strongly opposed to the oncoming war.  Its literature was banned from army barracks and members barred from the officer corps.

On the 25th of July, several days after the Austrian ultimatum to Serbia, the leading SDP newspaper published this:

… the class-conscious proletariat protests in the name of humanity and culture against the criminal actions of those agitating for war … Not one drop of German blood should be sacrificed for the power-hungry Austrian rulers and the imperialistic profit interests. (see more)

Throughout the following week, up until the imposition of censorship with the state of siege on July 31, SDP newspapers continued to describe the horrors of war, continued to argue that Germany should not fight for Austria.