Text: In that year, there were four emperors (Nero, Otho, Galba, and Vespasian), and the secret of the Roman Empire--that in a time of turmoil, a provincial commander with an army could march on Rome and become emperor--was revealed, but Rome's decline was a long way off.
Entailment: There were four emperors in that year.
Contradiction: Nero was the emperor for the entire course of that year.