Complex sentence: Ben-Dov believed in a theory of active redemption-that the mashiach would only come through a bloody national conquest, and that Jews who believed non-violent means could bring about the end of days were naive.
Split into simpler sentences: Ben-Dov believed in a theory of active redemption. He believed that the mashiach would only come through a bloody national conquest, and that Jews who believed non-violent means could bring about the end of days were naive.