An intellectual with anti-Fascist ideas, Mucchi was a sympathiser of the Corrente di Vita movement. In 1943, at the outbreak of the Italian Civil War he joined the Val d'Ossola partisans by enrolling in the 186ª Brigata Garibaldi. At the end of World War II he returned to Milan and started working in a Realist style. He also continued to work in the field of architecture, which he had begun to do in the 1930s. In 1947 he participated in the housing project for the QT8 area in Milan, for which he also designed furniture. His work was exhibited in the 8th Milan Triennale that same year. In 1956 he was invited to teach painting at the Academy of Arts, Berlin, where he spent a long time during the following years. He continued to hold exhibitions both in Germany and Italy, and to pursue his career as a decorator and illustrator. In 1967 he illustrated the Italian edition of Voltaire’s "Candido".