Complex sentence: Between 1848 and 1851, the repressive regime of Ferdinand II caused many to go into exile while an estimated 15,000 to 40,000 suspected revolutionaries or dissidents were jailed, most in appalling conditions.
Split into simpler sentences: Between 1848 and 1851, the policies of King Ferdinand caused many to go into exile. Meanwhile, an estimated 15,000 to 40,000 suspected revolutionaries or dissidents were jailed, most in appalling conditions.