Sometimes confused with the similar state-sanctioned military campaign known as an Imperial Crusade, a War of Faith differs in both who commands it and who participates in it.
An Imperial Crusade is declared on the order of the secular rulers of the Imperium, the High Lords of Terra or the Lord Commander of the Imperium, and involves multiple branches of the Imperial military, including the Adeptus Astartes, the Astra Militarum, the Imperial Navy and administrative support provided by the rest of the Adeptus Terra and the Ministorum.
A War of Faith, however, is declared on the sole spiritual and temporal authority of the reigning ecclesiarch of the Adeptus Ministorum and often includes only the military forces under the control of the Ministorum. These include the Frateris Templar before the Age of Apostasy and the Frateris Militia and the Orders Militant of the Adepta Sororitas since the 36th Millennium.
However, despite this distinction, Wars of Faith and Imperial Crusades often overlap in many ways and both will be employed to seek the conquest of new territory, retake worlds lost to enemies of the God-Emperor, purge rebels or Heretics to the Imperial Creed, and eradicate xenos and mutants who threaten Mankind.
Wars of Faith have also sometimes been declared against factions within the Adeptus Ministorum itself who have been deemed heretical or too radical to be tolerated even by the relatively wide bounds of the Imperial church's theological orthodoxy.
Wars of Faith have been declared concurrently with an Imperial Crusade and thus are also sometimes carried out by other Imperial armed forces outside of the Adeptus Ministorum, such as the regiments of the Astra Militarum. But when a War of Faith involves only the forces of the Ministorum, it is funded and directed solely by the resources of the Ecclesiarchy.
Though a War of Faith is initiated and financed on the order of the ecclesiarch, he or she does not have total control over the course or direction of a War of Faith. If they so choose, the High Lords of Terra can intervene in a War of Faith, though they usually refrain from doing so with Wars of Faith that only concern internal matters of the Ministorum.
The first War of Faith in Imperial history was called early in the 32nd Millennium against a rival religious faction to the Temple of the Saviour Emperor which was the predominant sect of the faith that believed the Emperor of Mankind to be a god and eventually evolved into the state-supported Adeptus Ministorum.
That rival sect was known as the Confederation of Light, which had also emerged from the period after the Horus Heresy on the world of Dimmamar and worshiped the Emperor as a divinity.
However, the Confederation believed that the Emperor's sacrifice after the Siege of Terra should serve as an example of true selflessness to everyone, and promulgated ideals of generosity, material frugality and humility towards one's fellow men and women.
Such ideals directly contradicted the beliefs of the Temple of the Saviour Emperor and the later Ecclesiarchy, which instead taught that the Imperium represented Mankind's divinely-ordained dominion over the universe, and that as the representatives of the God-Emperor in the mortal realm, it was the Adeptus Ministorum and its agents which should hold ultimate secular AND spiritual power.
In this view, the Emperor's sacrifice had been necessary to maintain Human domination of the galaxy, and talk of selflessness and generosity took a decided back seat to the Ministorum hierarchy's concerns about increasing its own wealth and political power within the broader structure of the post-Heresy Imperium.
By early in the 32nd Millennium the power of the Temple of the Saviour Emperor as embodied within the newly recognised state church that was the Ministorum was absolute, and only the adherents of the Confederation of Light represented an alternative version of the Emperor's faith that still found purchase among the people of the Imperium.
To curb this perceived threat to the Ministorum's popularity, and thus its political power, the ecclesiarch of that time managed to get a unanimous vote of the Senatorum Imperialis to approve what was the first War of Faith against their rivals.
The Confederation of Light was declared an organisation of Heretics and on the order of the High Lord of Terra, the Astra Militarum and the Imperial Navy were dispatched to assault Dimmamar, still the nexus of the Confederation's activities, and eradicate this "spiritual threat" to the souls of the Emperor's faithful.
Though some of its followers managed to escape or go underground on Dimmamar where they would eventually reemerge during the Reign of Blood of the Age of Apostasy in the 36th Millennium to lead a Reformation of the Ecclesiarchy, the Confederation of Light ceased to exist as a powerful alternative force within the early Imperium. The political dominance of the Adeptus Ministorum of that period over the Emperor's realm was then absolute, essentially rendering the Imperium a theocracy.
This first War of Faith would provide a template for the future, though as the Ministoum's power waxed over the next four standard millennia, it developed its own military forces and increasingly ignored the whims of the High Lords when declaring its own Wars of Faith -- as often directed at internal political enemies of the reigning ecclesiarch and cardinals as at true foes of the Emperor.
Ironically, however, the number of Wars of Faith would reach their peak during the Age of Redemption in the 37th and 38th Millennia, after the Imperial church had been reformed by the reemergence of the Confederation of Light under Sebastian Thor and the restoration of its more humane ideals and the belief that the Ministorum should support the Imperium's secular authorities, not dominate them.
Notable Wars of Faith
- War of the Beast
- Benedictine War
- War of the Confessor
- Cataclysm of Souls
- Orpheus Revolt
- Promethean War
- War for Piety
- Defence of Dimmamar
- Second Tyrannic War
- Defence of San Leor
- Codex: Adepta Sororitas (8th Edition), pg. 13
- Codex Adeptus Astartes - Space Marines (8th Edition), pg. 45
- Codex: Dark Angels (6th Edition), pp. 36-37
- Codex: Sisters of Battle (2nd Edition), pp. 6, 12-16
- Codex: Sisters of Battle (5th Edition), pg. 93
- Dark Heresy: Blood of Martyrs (RPG), pg. 43
- Imperial Armour Volume Twelve - The Fall of Orpheus, pp. 20-22
- Warhammer 40,000: Rulebook (5th Edition), pp. 124-126
- Warhammer 40,000: Rulebook (6th Edition), pg. 169
- White Dwarf 379 (US), pg. 93