Havemann joined the Communist Party of Germany (KPD) in 1932 and was one of the founders of the resistance group, European Union.

He received a death sentence for treason, but his execution was continually postponed because of the intervention of former colleagues, who insisted that Havemann was as important due to his work on chemical weapons and that he was still needed to explain the research.

He published articles in Sinn und Form criticizing modern socialism and revisionist works of the Western authors.

[3] In 1963 he lectured on 'Scientific Aspects of Philosophical Problems' (published as 'Dialectic without Dogmatism—Natural Sciences against Communistic Ideology') and was expelled from the ruling Socialist Unity Party and dismissed from the University—officially because he gave an interview to a newspaper from West Germany.

In 2005, Havemann was awarded the title Righteous among the Nations by the Israeli Holocaust memorial, Yad Vashem.