In 1913, Carl Windhoff, Fritz Kater, and he were the FVdG delegates at the First International Syndicalist Congress in London.
Programm, Ziele und Wege der "Freien Vereinigung deutscher Gewerkschaften" (What do the Syndicalists want?
The program summarized the FVdG's theory: a reaffirmation of the importance of strikes as a vehicle for emancipation and a rejection of the centralized mainstream labor unions.
In late 1918, Rudolf Rocker returned to Germany, in March 1919 he joined the FVdG and started gaining influence.
An avowed communist anarchist and follower of Kropotkin, Rocker rejected such close collaboration with Marxists.