Complex sentence: He was arrested in Besançon in September 1941 while attempting to see his son, but after six months of forced labour with the assistance of a German officer got the necessary papers to escape back to Marseille.
Split into simpler sentences: He was arrested in Besançon in September 1941 while attempting to see his son, and was sentenced to six months forced labour. With the assistance of a German officer he got the necessary papers to escape back to Marseille.