{{Otherusesotheruses|USE=Loyalist guerrilla actions|OTHERUSE=[[World Eaters]]/[[Word Bearers]] actions post-[[Battle of Calth]]|OTHERPAGE=Shadow Crusade}}{{otheruses|USE=Heresy-era battlebattles|OTHERUSE=Inquisition campaign|OTHERPAGE=Shadow War}}The '''{{PAGENAME}}''' refers to a series of small-scale and clandestine conflicts during the [[Horus Heresy]].

As the main battles of the Heresy waged, the Shadow Wars were fought largely unseen. The Shadow Wars were not fought by conventional [[Space Marine Legion]] fighting units. Rather, they were fought entirely apart from any structured authority or grand strategy. Most of the loyalist forces in the Shadow Wars were ad hoc and secretive forces, such as surviving bands of Astartes from the [[Shattered Legions]], the [[Knights-Errant]], and the [[Blackshields|Blackshield]]swarbands. Over the course of the Heresy, these small irregular units undertook thousands of separate engagements against the traitors loyal to [[Warmaster]] [[Horus]].{{Fn|1}} In one of the Sectors of the [[Segmentum Solar]] - [[Quintillus Sector]] - Shadow War raged for over 6 years, where nearly all Legions were inevitably drawn, some in a great scale armies, some - in just a small squads.{{Fn|2}}

*The [[Battle for of Honourum]]*Campaign in the [[Quintillus Sector]] just outside of the [[HonourumSegmentum Solar]]— war raged there for over 6 years, and nearly all Legions were inevitably drawn, some in a great scale armies, some - only in small squads.{{Fn|2}}

*{{Endn|1}}: [[The Horus Heresy Book Six- Retribution]] , pgs. 13-2113–21