A good deal of actual history combined with fiction. Each season covers an aspect of what was going on besides WW1 ending. Season one and two with the IRA. Season 3 with the Bolsheviks. Season 4 with the Black Hand and season 5, the start of facism in Europe and Oswald Mosley. I enjoyed the first 2 seasons the most because of the chemistry between Tommy and Grace and the choice Grace had to make. My favorite show. The modern music and cinematography are great.