Event · M41–M42
Battle of Thessala
The Battle of Thessala is a Warhammer 40,000 engagement in which Roboute Guilliman of the Ultramarines was wounded by the Chaos-aligned primarch Fulgrim. Orrery places it at the turn between the 41st and 42nd millennia, the period in which the Imperium under Guilliman’s regency was contending with the forces of Chaos, and anchors it to the map at Thessala. The surviving account is narrow: the confrontation between two primarchs is recorded, but the wider strategic circumstances are described only in outline. The principal participants are the two primarchs and the forces that followed them. Guilliman, Lord Commander of the Imperium and the Ultramarines’ primarch, is recorded as the Imperial commander. Fulgrim, formerly of the Emperor’s Children and long since a servant of Chaos, is recorded as the opposing leader. Their meeting recalls the enmity between loyalist and traitor primarchs that began in the Horus Heresy, and it is consistent with the wider pattern of Chaos commanders seeking out the Imperium’s leadership during the Indomitus Crusade. The exact size and composition of the forces on either side, and the immediate cause of the engagement, are not established here and are left unstated rather than supplied. The outcome is recorded chiefly through its effect on Guilliman, who was wounded by Fulgrim. On the Orrery timeline this makes the battle a point of contact between the Ultramarines’ primarch and the Emperor’s Children’s former primarch, and a useful neighbour to the Indomitus Crusade and to Guilliman’s own dossier. Accounts of the duration, the casualties and the fate of Thessala afterwards are not attested in the material this entry follows, and later tradition may refine them.
See where Battle of Thessala occurred on the galactic map in the 41st Millennium.