He was impressed by 12 Byzantine Rulers, a podcast by Lars Brownworth,[2] however, he struggled to find anything similar on the history of Rome.

Duncan had a longstanding interest in Roman history and was reading The War With Hannibal by Livy at the time.

[3] He enjoyed many of the historical episodes he encountered in the book, but realized that much of the public knew little about Rome outside of Caesar and Augustus' time.

[5] Duncan has mentioned that in making the podcast, he learned "human nature has changed very little," and that people generally respond to the same situations in the same sorts of ways.

The book is a collection of edited transcripts from the first 46 episodes of the podcast, covering the time period from the founding of the Roman Kingdom through the breakdown of the Republic.

It focused on the period between the rise of the Gracchi Brothers through Sulla's Civil War, which is covered in Episodes 29 through 34 of the THoR podcast.

[11] The series proved popular enough that six years after the podcast ended, Duncan released two sets of appendix THoR episodes that covered topics he had not been able to properly address in the main series, and which he had learned a lot about through the research for The Storm Before the Storm.