Complex sentence: After the violent deaths of Tiberius Gracchus in 133 BC and Gaius Gracchus in 121 BC, political violence in Rome continued to intensify, soon becoming the norm and not the exception Lutz (2006) p.502.
Split into simpler sentences: After the violent deaths of Tiberius Gracchus in 133 BC and Gaius Gracchus in 121 BC, political violence in Rome continued to intensify. Political violence soon became the norm and not the exception Lutz (2006) p.502.