By the time of the Berlin syndicalist conference, the libertarian leadership of the CGTU was already being challenged by a growing communist faction, led by
Pierre Monatte, which had recovered from its disorientation and prepared to take over the CGTU. As the RILU had so far only managed to secure the affiliation of small, minor unions, it focused its recruiting efforts on the CGTU, despite its concerns about the strong libertarian and anti-statist influence over the organisation. The Bolsheviks directed the
French Communist Party (PCF) to rally support for the RILU within the CGTU by
infiltrating its trade unions, attacking the libertarians in their publications and forming alliances with other pro-communist factions. Communists denounced the libertarians for taking over the leadership of the CSR, for their role in the Berlin conference and for their withdrawal of support for the Russian Revolution. accused the delegates to the Berlin conference of exceeding their mandate and deliberately sabotaging the affiliation with the RILU. At the St. Etienne congress of the CGTU, RILU general secretary
Solomon Lozovsky promised the organisation that affiliation between it and the PCF would not be mandatory and that its autonomy would be respected by the RILU. Two resolutions on international affiliation were put before the congress, one by the libertarian
Pierre Besnard and the other by the communist
Gaston Monmousseau: the former called for the creation of an independent trade union international, without any links to the Communist International; the latter advocated for the CGTU to affiliate with the RILU, provided its autonomy would be respected and no reciprocal representation required. With the support of the pro-communist faction, Monmousseau's motion was carried and the new political bureau of the CGTU was brought under the control of the
Vie Ouvrière group, with the PCF declaring it a "brilliant victory for the party". Although the RILU agreed to drop the condition of "reciprocal representation" between the RILU and the CI, it insisted that communist parties would take a "leading role" in the unions affiliated with the RILU. Nevertheless, the leadership of the CGTU agreed to these terms and finalised its affiliation with the RILU. The
libertarian minority subsequently formed the Syndicalist Defense Committee (; CDS), which acted as an internal opposition within the CGTU, aiming to reassert libertarian control over the union. The CDS called for the complete independence of trade unions from political parties and expressed support for the establishment of a syndicalist international. The bureau of the RILU expressed hope that, in the interest of unity, the CDS would change its mind. Although RILU general secretary
Solomon Lozovsky publicly disregarded the CDS as an unimportant splinter group, in his private correspondence with Pierre Monatte, he called for the organisation to be destroyed "with fixed bayonets" and insisted that each issue of
La Vie Ouvrière and ''L'Humanité'' carry
hit pieces against it. ==International relations==