The Siege of Terra (Gav Thorpe) Books in Order

The Siege of Terra is the final campaign of the Horus Heresy. Horus has brought his rebel armies to the Solar System, the Emperor is trapped on the Golden Throne, and the Imperial Palace has become the last line between humanity and total defeat.

Gav Thorpe's The First Wall is the third novel in the Siege of Terra sequence. It moves the focus from the outer defences to the Palace itself, where Rogal Dorn's fortifications finally face the full force of Perturabo and the Iron Warriors.

Walls are not just stone in this war.

The central military struggle is the battle for the Lion's Gate Spaceport. The traitors need it to land their heaviest weapons on Terra. Dorn knows that if the spaceport falls, the siege will become even harder to contain. That creates a direct contest between two primarchs whose identities are tied to engineering, discipline, and the art of war.

But the novel is not only about the two commanders. The Siege is too large for that. The First Wall follows defenders and attackers at several levels, from the vast plans of the primarchs to the soldiers and civilians caught inside a city built for an apocalypse. As the fighting intensifies, the Neverborn are drawn toward the slaughter, making the battlefield stranger and more dangerous.

The tone is relentless. This is not a story about a clean charge or a decisive duel that fixes everything. It is about attrition, exhausting logistics, exhausted people, and the terrible work of holding a position when every calculation says the enemy should eventually break through.

The book works best after the opening Siege of Terra novels, especially The Solar War and The Lost and the Damned. Those books establish how Horus reaches Terra and how the defenders begin to prepare for the assault. Still, The First Wall has a focused enough objective that readers interested in the Imperial Fists or Iron Warriors can approach it as a major battle within the larger finale.

Start with The Solar War for the full Siege of Terra experience. If you are following Gav Thorpe's work specifically, read The First Wall when you want the campaign to reach the Palace walls and the rivalry between Dorn and Perturabo to become brutally practical.