Among the many conflicts that have taken place throughout its history, some stand out as truly monumental, shaping the course of events and leaving an indelible mark on the lore of the setting.
In this article, we’ll take a look at 10 of the biggest battles in Warhammer 40K, from the earliest days of the Imperium to the most recent conflicts fought in the far reaches of the galaxy.
10) Battle of Macragge
The Battle of Macragge was the first major battle fought between the Imperium and Chaos during the Horus Heresy. It took place on Macragge, homeworld of Roboute Guilliman and his Ultramarines Space Marine Legion.
The Ultramarines were defending their world from an assault by Abaddon’s Black Legion and other Traitor Legions under their Primarch Horus Lupercal.
The battle lasted for three weeks, during which time both sides suffered heavy losses but neither could gain an advantage over the other until Roboute Guilliman himself arrived with reinforcements from nearby Ultramar system worlds such as Espandor and Konor Prime.
9) Battle of Ichar IV
The Battle of Ichar IV was a major conflict between the Imperium of Man and its Ork foes, which took place in 976.M41. The planet was home to an Adeptus Mechanicus Forge World, one of the largest production centers for war materials in the galaxy.
It was also a vital strategic location due to its proximity to Terra itself; if it fell into enemy hands then it could be used as a staging area for future attacks on humanity’s homeworld by Orks or other enemies of mankind (such as Chaos).
The invading Orks were led by Warboss Garshul and his War Horde who had come from their home world Charadon seeking new territories upon which they could expand their empire.
Their first target was Ichar IV where they hoped to find easy prey amongst an unsuspecting population who had never before encountered such fierce creatures before them; however, this proved not quite true when they encountered resistance from Imperial forces led by Lord General Zyvan himself!
8) Battle of Armageddon
The Battle of Armageddon was a major conflict fought between the Imperium of Man and the Ork Waaagh! led by Warlord Ghazghkull Mag Uruk Thraka. The battle took place on the Hive World of Armageddon in 998.M41 and resulted in one of the greatest losses suffered by the Imperial Guard since their inception as an independent fighting force during Old Night.
The Ork invasion force consisted of more than 100 million Greenskins, including many thousands of war machines such as Stompas, Deff Dreads and other vehicles. The Orks landed on Armageddon Prime with little warning and began to spread out across its surface.
They were able to capture large swathes of territory before being stopped by three Space Marine Chapters: the Blood Angels, Salamanders, and Ultramarines.
Despite these early successes at repelling them from their landing sites, however; Ghazghkull’s forces soon began pushing back against these counterattacks thanks largely due to their sheer numbers advantage over those defending against them (which included only about half as many troops).
7) Battle of Cadia
The Battle of Cadia was a major conflict that took place in the Cadian Sector, pitting the forces of Chaos against those of the Imperium. It was one of many battles fought during Abaddon’s 13th Black Crusade, which saw him attempt to conquer Cadia and thus open up a new front in his war against Terra itself.
The battle began when Abaddon launched an attack on Cadian space with his vast fleet; this included numerous Chaos ships as well as Traitor vessels from various Imperial Navy fleets and even from their own forces.
The first wave consisted primarily of World Eaters under Kharn himself; these were followed by Word Bearers led by Lorgar himself who had been sent ahead by Horus after he fell at Isstvan V so that they might secure the planet for him before he arrived himself (he did not).
6) Battle of the Beast’s Eye
The Battle of the Beast’s Eye was a major conflict that took place on the planet Kastorel-Novem in 811.M41. The battle was fought between a large force of Orks under Warboss Grog Ironteef and an Imperial Guard regiment led by Colonel Schaeffer.
The Orks were attempting to take control of an ancient Eldar structure known as the Beast’s Eye, which had been built around an enormous Warp portal leading directly into their domain — and they almost succeeded!
The Imperial Guard forces were outnumbered five to one by their green-skinned opponents, but they held out long enough for reinforcements from other worlds in this sector to arrive and drive off their enemies with heavy losses on both sides (although many more casualties were suffered by Grog Ironteef’s army than those loyalist troops).
5) Battle of Medusa V
The Battle of Medusa V was a major conflict between the Imperial Guard and the Tyranids on Medusa V, an Imperial planet in Segmentum Pacificus. It was fought during the First Tyrannic War (also known as Hive Fleet Behemoth).
The battle began when Hive Fleet Behemoth arrived at Medusa V in 992.M41 and landed its troops on the surface of the planet. The main force consisted of three Tyranid broods supported by one winged hive tyrant and two carnifex brood nests, which were quickly deployed by landing craft as soon as they reached orbit.
The initial wave suffered heavy losses due to anti-aircraft fire from Imperial ships in orbit above Medusa V but eventually managed to establish a beachhead on land using their organic drop pods.
3) Battle of the Gothic War
The Battle of the Gothic War was the first major conflict of the Horus Heresy, a galaxy-wide civil war that would eventually lead to the destruction of all but one of humanity’s galactic empires.
The battle began when Warmaster Horus, who had been corrupted by Chaos and led his traitorous forces against those loyal to Emperor Sanguinius, attacked Ultramar in an attempt to capture its worlds and destroy its fleet.
2) Battle of Tallarn
The Battle of Tallarn was a conflict between the forces of the Imperium and the Iron Warriors Space Marine Legion. It took place on the desert world of Tallarn, in which both sides fought for control over a vital strategic location: an intact starport.
The Iron Warriors had been ordered to destroy all Imperial facilities on Tallarn as part of their campaign against Rogal Dorn’s Imperial Fists Chapter, but they were stopped by an unlikely alliance between elements within their own ranks and those belonging to other Legions who opposed Horus’ rebellion against Emperor Roboute Guilliman’s rule over humanity’s empire.
The battle lasted for several months and saw millions die before it ended with an Imperial victory thanks largely to help from Eldar allies who had come at request from Leman Russ (who later became known as “the Great Wolf”).
1) Battle of Holy Terra
The Battle of Terra was the final and most decisive conflict of the Horus Heresy, fought between the forces of the Imperium and the Traitor Legions of Chaos led by Warmaster Horus. It took place on Terra itself, the very heart of humanity’s empire and the seat of its rulership.
The battle lasted for several months and saw the destruction of much of the planet’s surface as well as the deaths of billions of people.
In the end, it was the loyalist forces under the command of the Emperor himself who emerged victorious, but at a great cost: the Emperor was mortally wounded and forced to enter into a state of suspended animation, while Horus was killed and his forces scattered to the winds.