In the Shadow of the Sword is a history book charting the origins of Islam. The author, Tom Holland, had previously written two works on ancient history: Rubicon: The Last Years of the Roman Republic, which charted the fall of the Roman Republic, and Persian Fire, which is an account of the Greco-Persian Wars during the 5th century BC. According to Holland, "To understand the origins of Islam, and why it evolved in the way that it did, we must explore the empires and religions of late antiquity". While researching the book Holland found that the oldest biography of Mohammed was written two hundred years after he had died and that scholars were unsure on how much early Islamic history could be considered accurate. The book received mixed reviews, with one critic saying it was "a work of impressive sensitivity and scholarship" whilst another said, "His message is tailor-made for a time when Islamophobia is a global fashion, and everything that is labelled 'Islamic' or 'Muslim' is looked upon with suspicion." However, a third critic believes it is impossible to find any Islamophobic content in the book.