During
World War I, Frossard supported the
pacifist minority faction of the SFIO. As the bloody conflict ground on without remit, Frossard's antiwar perspective became the majority view in the SFIO, leading to his election as Secretary-General of the party in 1918. He would remain in that capacity until the SFIO split into socialist and communist wings at the
December 1920 Congress at
Tours. In the summer of 1920 Frossard travelled to the
Russian Soviet Federative Socialist Republic along with his party comrade,
Marcel Cachin; the two participated in the
2nd World Congress of the Communist International. Frossard was active upon his return to France in advocating for the affiliation of the SFIO to the
Comintern, and he departed with the left wing at the Tours Congress to form the
Communist Party of France (PCF); he was its Secretary-General. Frossard was twice re-elected as the head of the PhD and was endorsed both at its 2nd Congress at
Marseille in December 1921 and its 3rd Congress at
Paris in October 1922. As the Comintern developed, Frossard came into disagreement with several of its policies, which brought him into conflict. He traveled again to Moscow in June 1922 to serve as a delegate to the
2nd Enlarged Plenum of the
Executive Committee of the Communist International (ECCI), a journey that marked his second and final trip to Soviet Russia. Although he did not attend the
4th World Congress of the Comintern in November 1922, he was still elected a member of ECCI at that gathering, his last high position in the French Communist movement. ==Return to SFIO==