Complex sentence: Semenov and Ungern, though fervently anti-Bolshevik, were not part of the White movement and Semenov refused to recognize the authority of Admiral Aleksandr Kolchak, the nominal leader of the Whites in Siberia.
Split into simpler sentences: Semenov and Ungern, though fervently anti-Bolshevik, were not part of the White movement. In addition, Semenov refused to recognise the authority of Admiral Aleksandr Kolchak, the nominal leader of the Whites in Siberia.