Born in Berlin as the son of a postal worker, Willi Eichler became a clerk and fought in the First World War. In 1919 he joined the Social Democratic Party (SPD). Shortly afterwards, he became the private secretary and one of the closest confidants of Leonard Nelson, who had created an International Youth League in 1917-18 as a new educational community based on principles of Lebensreform (a movement advocating a new way of life). Nelson’s close colleagues included the educationist Minna Specht and the journalist Mary Saran. When the Youth League was expelled from the SPD because of political differences, the Internationale Sozialistische Kampfbund (ISK - International Socialist Combat League) was formed. After Nelson’s death in 1927, Eichler took over as chairman of the ISK and published the theoretical party organs “isk - Information Journal of the International Socialist Combat League” and “Der Funke” (The Spark). In November 1933 Eichler had to flee from National Socialist Germany. He established an exile center in Paris to support clandestine ISK groups in Germany. In the following years Eichler concentrated on journalism and publishing in the struggle against the National Socialist regime. In April 1938 he was expelled from France because of his political activity, but found asylum in London, where he headed a small ISK group and published ISK journals and pamphlets. In 1941 Eichler and his Combat League joined the Union of German Socialist Organizations in Britain, and as a member of its executive committee he inaugurated the unification with the SPD in August 1945. He also became a member of the National Group of German Labor Unionists in Britain. Eichler returned to Germany at the beginning of 1946. He was regarded as an influential SPD theoretician and as father of the Godesberg Program. Willi Eichler died in Bonn in 1971.