The Battle of Pluto was the first major engagement of the Solar War during the Horus Heresy. It saw the Alpha Legion attempt to cripple the Sol System’s defences, only to be stopped by Rogal Dorn and the Imperial Fists.
Background: the Solar War begins
After Horus turned traitor, he needed to clear a path to Terra. The Sol System was fortified and watched over by Rogal Dorn and his Imperial Fists, with Mars still under blockade after the Mechanicum civil war.
Horus gave Alpharius and the Alpha Legion a simple job: cause chaos across Sol before the Warmaster arrived. The Alpha Legion specialised in infiltration, so they were the obvious choice.
The infiltration of Sol
Alpharius didn’t use Warp travel. Instead, he put his entire fleet into stasis and let it drift towards Sol for a year, powering down to hide its heat signature. The ploy worked, and the fleet reached the system’s edge undetected.
Meanwhile, sleeper cells planted years earlier activated. A freighter exploded over Terra, killing millions. Rebels hit Damocles Starport, and an uprising erupted on Triton. These were distractions, though. Alpharius’ real target was Pluto, the linchpin of the loyalist surveillance network.
The battle itself
With Dorn pulled in different directions, the Alpha Legion struck. Over 200 warships, led by the Alpha, hit Pluto and its moons: Charon, Styx, Nix, Kerberos, and Hydra. Uprisings broke out on the surface as the fleet arrived.
The fighting was brutal. The Alpha Legion had surprise and numbers, but the Imperial Fists had Dorn. He led a counter-attack that broke the traitor fleet. Alpharius was killed in the fighting, and the Alpha Legion retreated.
- Loyalists: Imperial Fists, Inferallti Hussars, Black Sentinels
- Traitors: Alpha Legion
- Loyalist commanders: Rogal Dorn, Archamus, Sigismund
- Traitor commanders: Alpharius, Kel Silonius, Ingo Pech
Aftermath and legacy
The loyalists won, but it was costly. Several Imperial Fists captains died, including Archamus. The Alpha Legion’s failure to take Pluto meant the loyalists kept their eyes on the system, which mattered later in the Siege of Terra.
The battle also settled a score. Alpharius had long claimed he could beat Dorn. He was wrong.
Key facts
- The Battle of Pluto was the first major engagement of the Solar War.
- Alpharius infiltrated the Sol System by drifting in stasis for a year.
- The Alpha Legion attacked with over 200 warships against Pluto and its moons.
- Rogal Dorn led the loyalist defence and killed Alpharius.
- The loyalists held Pluto, keeping their surveillance network intact.
FAQ
Who won the Battle of Pluto?
The Imperial Fists and their allies won. The Alpha Legion was forced to retreat after Alpharius was killed.
Why did the Alpha Legion attack Pluto?
Pluto was the key to the loyalist surveillance network in the Sol System. Taking it would have blinded the defenders before Horus arrived.
When did the Battle of Pluto happen?
It took place around 010.M31, at the start of the Solar War during the Horus Heresy.