That year, the CGTU merged into the General Confederation of Labour, and Jourdain joined the Paris regional union of metallurgists, part of the Metalworkers' Federation (FTM).
He was elected as the union's secretary in 1938, but in 1939 was called up to serve in the French Navy, working at the seaplane base in Etang de Berre.
[1] Returning to France, Jourdain was immediately asked to represent the reformed FTM, and in 1946, he was appointed as the union's secretary, with responsibility for aviation.
These activities led him to prominence, and in 1949, he was elected as the first general secretary of the Trade Union International of Workers in the Metal Industry.
[1] By 1973, Jourdain's health was declining, and he moved to lead a PCF commission on the party structure in large companies, but in 1975, he also left this activity.