Well before Praetorian of Dorn was released speculation had begun about how many books the Heresy series would include. Frequently, these conversations would hinge around which Legions had yet to star in their own novel, the assumption being that each of the eighteen would get their turn in the limelight before the series reached the Siege of Terra. As the series closed in on forty installments the absence of a novel focusing on Rogal Dorn and his Imperial Fists became more and more conspicuous, and yet Praetorian of Dorn still came as a surprise because it unexpectedly pitched the Fists against the Alpha Legion. In hindsight however this match up makes perfect sense, as the insidious Alpha Legion are the perfect choice to weaken the Sol system's defenses ahead of Horus's invasion. Praetorian of Dorn covers the opening phase of this 'Solar War', the war-within-a-war that took place as the traitor noose closed around the very heart of the Imperium.
The Solar War is the final phase of the Horus Heresy, the last theatre to be fought in before the traitors reach the Imperial Palace. The cynic in me believes this theatre of conflict was invented so that Black Library could stall there for a bit while they tie off all the loose ends the Heresy series has created, but from a lore perspective it makes perfect sense and John French gets it off with a bang as the Alpha Legion launch a series of coordinated strikes against Terra. In a delightful act of foreshadowing the novel's protagonist, veteran Imperial Fist Archamus, interprets this as the first act of Horus's final attack and triggers the appropriate protocol, but Dorn sees the truth and tasks Archamus with hunting down the traitor operatives loose in the Sol system. The pace of the novel slows down a bit as Archamus and the operatives play cat-and-mouse, but everything builds to an explosive climax when an Alpha Legion fleet drifting in the void is reawakened and launches a full-scale assault on Pluto.
There are many things to like about Praetorian of Dorn, least of all that it is John French's first Heresy novel after years of contributing short stories. French pays tribute to his first Heresy short by including his remembrancer character Solomon Voss in one of three flashbacks that break up the book, the first covering Archamus's Astartes training, the second a battle against Orks during the Great Crusade and the last an ambiguous confrontation between Dorn and Alpharius. The flashbacks give the novel its structure, adding depth to Archamus and advancing the book's themes despite taking the story backwards chronologically. The last flashback is the shortest but contains my favourite moment from the whole book: Dorn revealing that he has a mastery of stealth and terror tactics at least equal to Alpharius's own but chooses not to employ them, stating that the primarchs, at least in his eyes, are all what they want to be rather than what they were made to be. This one line has huge ramifications for the lore.
Praetorian of Dorn is not quite the novel some wanted; despite its Imperial Fist main character it does not explore the Legion as a whole and is just as concerned with the Alpha Legion infiltrators as it is with the sentinels of Terra. However, it is the novel we needed without knowing it. The action is intense, the main characters are compelling and the finale contains the biggest unexpected treat of all: a primarch killing a primarch. Praetorian of Dorn is an essential read.
