He was given responsibility for constructing a new union headquarters, in Leipzig, and was appointed as regional secretary for most of southern Germany, developing new branches in the Rhineland.
At the end of 1905, he became acting president, when Bruno Poersch resigned, and in April 1906, he was elected to the office on a permanent basis.
[1] He organised a conference in 1907 which formed the International Secretariat of the Workers in Public Services (PSI), and he became its general secretary.
With the outbreak of World War I soon afterwards, Heckmann argued that the PSI should be abolished, and Mohs could return to his old post as leader of the union's southern district.
The VGS left the PSI at the start of 1917, but Mohs remained in post, and persuaded the union to rejoin in 1919.
He then retired from the international position, and won election as a district councillor in Schöneberg, with responsibility for the local employment office.