Complex sentence: Moreover, since Pol Pot was the recognised communist leader of Cambodia his influence did not vanish, and for instance, he was able to order the arrest and execution of former NADK Supreme Commander Son Sen in 1997.
Split into simpler sentences: Moreover, since Pol Pot was the recognized communist leader of Cambodia, his influence didn't vanish anyway. In fact, for instance, he was able to order the arrest and execution of former NADK Supreme Commander Son Sen in 1997.