In July 1914, he organized the anti-World War I rallies of the SPD and on 31 July and 1 August fought for the SPD to vote in the Reichstag against an increase in war loans.
U srpnju 1914. organizirao je antiratnu skupštinu SPD-a, a 31. srpnja i 1. kolovoza borio se protiv odluke u SPD-u da se povečaju ratne zasluge.