Shelley refers to Julius Caesar's empire-building through his military campaigns. According to Enlightenment historians, his conquests provoked a political crisis in Rome, and Caesar's assassination in 44 BCE marked the end of a more peaceful Roman Republic and the beginning of its Empire. Romantic liberals like the Shelleys, Leigh Hunt, and Lord Byron idealized the republic as a political form and set it against militaristic empire building. However, Mary Shelley is original in associating "domestic affections" with the idea of a republic based on reason.