Complex sentence: Barvinok, being a participant of the highest echelons of both the Russian Empire and the independent Ukraine, was a tempting target for the Soviets, but his prominence in numerous scientific circles made it difficult to arrest him personally.
Split into simpler sentences: Barvinok, being a participant of the highest echelons of both the Russian Empire and the independent Ukraine, was a tempting target for the Soviets. His prominence in numerous scientific circles made it difficult to arrest him personally.