Complex sentence: His family moved to France in the wake of the Spanish Civil War and, after the French defeat and subsequent Nazi occupation of France, Semprún joined the Communist resistance group "Francs-Tireurs Partisans".
Split into simpler sentences: His family moved to France in the wake of the Spanish Civil War. After the French defeat and subsequent Nazi occupation of France, Semprún joined the Communist resistance group "Francs-Tireurs Partisans".