Complex sentence: As leader of the Bielski partisans, his aim was not to attack railroads and roads that the German Nazis were using as supply routes, although there were some such attacks but to save Jews, who were under persecution from the Nazis during the Holocaust.
Split into simpler sentences: As leader of the Bielski partisans, his aim was not to attack railroads and roads that the German Nazis were using as supply routes. Although there were some such attacks to save Jews, who were under persecution from the Nazis during the Holocaust.