Complex sentence: Significant fake news stories can be traced back to Octavian's 1st century campaign of misinformation against Mark Antony and the forged 8th century Donation of Constantine, which supposedly transferred authority over Rome and the western part of the Roman Empire to the Pope.
Split into simpler sentences: Significant fake news stories can be traced back to Octavian's 1st century campaign of misinformation against Mark Antony. In the eighth century, a forged document became widely-circulated known as Donation of Constantine, which supposedly transferred authority over Rome and the western part of the Roman Empire to the Pope.