The so-called Second Battle of Paramar was an engagement of the Horus Heresy that took place in either 008.M31 or 011.M31, depending on the source, following the capture of the Paramar System by the Traitors in the First Battle of Paramar.
Several Terran years later, a mixed force of Loyalists consisting of the Legio Atarus (Firebrands), Legio Ignatum (Fire Wasps), Legio Solaria (Imperial Hunters), with ground assault units from the Blood Angels and White Scars Legions, clashed with the defending Traitors.
The Traitor forces were comprised of god-engines drawn from the Legio Fureans (Tiger Eyes) and Legio Mortis (Death's Heads) Titan Legions that were rearming and resupplying in the system after several Terran years of intensive campaigning, as well as extensive elements of the Sons of Horus and Word Bearers Legions.
The Loyalists conducted a series of diversionary attacks across the Paramar System in order to draw troops away from their true target, before conducting a full scale planetstrike against Paramar V's primary spaceport, the Paramar Nexus. They captured it intact and then pressed outwards to begin the destruction of the mass-provender silos containing wargear and vehicles that sprawled across the plateau beyond.
It was soon revealed, however, that the Traitors had seen through the ploy and prepared a huge counterattack force. Though they inflicted heavy damage on the provender silos before the Traitor counterattack hit home, the vast majority of the Loyalist invasion forces was surrounded and destroyed without mercy.
The Paramar System would remain in Traitor hands for the rest of the Horus Heresy. The servants of Chaos would only be dislodged from the system following the Third Battle of Paramar in 019.M31 during the vengeance campaigns of the Great Scouring.
The Horus Heresy - Book Three: Extermination by Alan Bligh states that the Second Battle of Paramar took place in 008.M31.
The timeline published in the Adeptus Titanicus: The Horus Heresy Rulebook in 2018 states instead that the campaign took place in 011.M31.
- The Horus Heresy - Book Three: Extermination (Forge World Series) by Alan Bligh, pp. 18-31
- Adeptus Titanicus: The Horus Heresy Rulebook (Specialty Game), pp. 14, 16