Fischer was a Trotzkyan communist, whose anti-Stalin leanings led in 1947 to his long-term, illegal imprisonment in Soviet gulags.
[1] He was freed with the Austrian "Staatsvertrag", treaty with the WWII allies in 1955, and returned to Austria, where he lived until his death.
Fischer died at age 44 from consequences of his imprisonment in KZ Buchenwald and Soviet gulags.
In 2013 Fischer was finally fully rehabilitated, as his convictions in the Austro-fascist stare had not had a legal basis for such step during his lifetime.
[2] Today, Fischer is used as a "moral" reference point in parts of the Socialdemocratic Party of Austria.