Complex sentence: Ungern took part in the Russian offensive in East Prussia, where in 1915-1916 he participated in rear-action raids on German troops by the L.N. Punin Cavalry Special Task Force.
Split into simpler sentences: Ungern took part in the Russian offensive in East Prussia. From 1915-1916 he also participated in rear-action raids on German troops by the L.N. Punin Cavalry Special Task Force.