‘The History of the Decline and Fall of the Roman Empire’ is a book of history written by the English historian Edward Gibbon (1737-1794). It traces the trajectory of Western civilization (as well as the Islamic and Mongolian conquests) from the height of the Roman Empire to the fall of Byzantium. The work covers the history of the Roman Empire, Europe, and the Catholic Church from 98 to 1590 and discusses the decline of the Roman Empire in the East and West. Gibbon offers an explanation for the fall of the Roman Empire, a task made difficult by a lack of comprehensive written sources, though he was not the only historian to attempt the task. According to Gibbon, the Roman Empire succumbed to barbarian invasions in large part due to the gradual loss of civic virtue among its citizens. They had become weak, outsourcing their duty to defend their empire to barbarian mercenaries, who then became so numerous and ingrained that they were able to take over the Empire. Romans, he believed, were unwilling to live a tougher, military lifestyle.