The Frateris Templar served as the primary military order of the Adeptus Ministorum for several centuries until it was disbanded in the 36th Millennium following the Reign of Blood of High Lord Goge Vandire during the Age of Apostasy. It was subsequently replaced as the Ecclesiarchy's primary military force by the Militant Orders of the Adepta Sororitas, better known as the Sisters of Battle.
The Frateris Templar were founded soon after the Ecclesiarchy moved its headquarters away from Terra and to the Cardinal World of Ophelia VII in order to escape the political domination of the Imperium's secular Administratum. With its previous restraints removed, the Ecclesiarchy began to rapidly grow in power within the Imperium's political structure, forming its own interstellar fleet and armies independent of the Imperial Guard and the Imperial Navy, which became known as the Frateris Templar. The Ecclesiarchy's forces included many commercial and military starships among their numbers, and dozens of Templar armies, each possessing the strength of an Imperial Guard Regiment. The Frateris Templar was an all-male military order and operated effectively as the private army of the Ecclesiarchy. At times it was used to crush revolts against the Ecclesiarchy's power and its religious domination of the Imperium.
The Age of Apostasy
Three hundred standard years after the Frateris Templars' founding in the early 36th Millennium, the Ecclesiarchy moved its central operations back to Terra after the insane High Lord Goge Vandire, Master of the Administratum, also seized the Ecclesiarchy as his own, becoming both Master of the Adeptus Administratum and the Ecclesiarch of the Adeptus Ministorum simultaneously. When a pious priest of the Imperial Cult named Sebastian Thor led the reforming Confederation of Light in revolt against Vandire's tyranny, Vandire sent the naval and ground forces of the Frateris Templar to destroy him and the Confederation, along with every living creature on the world of Dimmamar in the Segmentum Obscurus. However, en-route to Dimmamar, the Frateris Templar fleet was engulfed in a Warp Storm and destroyed, and the storm later came to be known as the Storm of the Emperor's Wrath because Sebastian Thor believed that the Emperor of Mankind's own will had been manifested in the creation of the storm because of his disgust for Vandire's attempt to seize power. Thor believed that this event was a sign that the Emperor desired the overthrow of Vandire and the reformation of the Imperium. After Vandire's defeat and the end of his Reign of Blood following the assault of the Confederation of Light and its allies among the Space Marines, the Adeptus Mechanicus and the Imperial Guard upon Terra, the Frateris Templar was disbanded by the new Ecclesiarch, Sebastian Thor, and the Adeptus Ministorum was barred by his Decree Passive from ever holding any men under arms. As such, the Templars' role as the military defenders of the Ecclesiarchy was taken over by the Militant Orders of the Adepta Sororitas, who also began to serve as the Chamber Militant of the Ordo Hereticus, the branch of the Imperial Inquisition charged with policing the Ecclesiarchy, as well as the rest of the Imperium, for heresy and treason.
- Codex: Sisters of Battle (2nd Edition)