After the May 1926 "Coup d'État, he opposed Piłsudski. He was arrested and beaten by the police and then sentenced in the 1931–32 Brest trials to two and a half year in prison. Rather than serving the sentence he emigrated to France. While abroad he supported the republican cause in the Spanish Civil War and published a critical response to Marcel Déat's pamphlet "Why Die for Danzig?" which advocated appeasement of Hitler.