Complex sentence: Tuvia kills the local Ukrainische Hilfspolizei chief responsible for his parents' deaths and the brothers stage raids on the Germans and their collaborators; however, Jewish casualties cause Tuvia to reconsider this approach because of the resulting risk to the hiding Jews.
Split into simpler sentences: Tuvia kills the local Ukrainian Auxiliary Police ("Ukrainische Hilfspolizei") chief responsible for his parents' deaths, and the brothers stage raids on the Germans and their collaborators. However, Jewish casualties cause Tuvia to reconsider this approach because of the resulting risk to the hiding Jews.