In 1951 he founded the arte nucleare movement with Sergio Dangelo, which unlike abstract art was overtly political. Baj himself was aligned with the anarchist movement. His most well-known pieces are probably the series of "Generals": absurd characters made from found objects such as belts or medals.
In 1972 public display of a major work, "Funeral Of The Anarchist Pinelli" (a reference to Carlo Carrà's famous painting The Funeral of the Anarchist Galli of 1911) was banned after the murder of the police officer believed to be responsible for Giuseppe Pinelli's death in custody. However his work continued to be political. In 1989 he designed thirty marionettes for Le bleu-blanc-rouge et le noir, an opera by Italian composer Lorenzo Ferrero to a libretto by Anthony Burgess, written for the bicentenary of the French Revolution. In his last years he created a series of paintings in protest at the election of Silvio Berlusconi. He died in Vergiate, Italy.Wikipedia