Great Crusade: Before the arrival of the Emperor's armies during the Great Crusade the Validus sector was home to a relatively large and powerful human empire. This ruler of this empire, a psyker, had visions of mighty warriors who were all identical saving the empire from a foul threat. These visions became truth when Ork forces started to pour into various worlds of the empire. What the ruler didn't know though was that the Orks were forced to retreat into the empire by crusading Alpha Legion. The warriors of Alpharius had been wiping out various Orks held worlds along the Flavonian Course and while many Orks simply faced these mighty warriors in battle, many simply fled to fight battles against weaker opponents.
When the Orks finally arrived in the Validus sector, the humans stood no real chance against their might. Having sensed this opportunity, Alpharius offered the empire of Validus salvation in return for submission to the Imperium. The Orks were quickly defeated and Validus was easily integrated into the Imperium.

Horus Heresy: After the annexation of the human empire the Alpha Legion forces quickly moved on into the Anargo sector and other sectors which were more difficult to conquer, what this meant for the Validus sector was that it remained relatively unaffected by the Horus Heresy. Forces from Validus poured into the surrounding sectors supporting loyalist forces against the traitors.

Age of the Imperium: In the years after the Horus Heresy Validus kept it's role of supporting the Imperial war effort throughout the Esquiline Quadrant. Various regiments of the Imperial Guard were sent from the spaceports in the Arius subsector to the Anargo Sector to fight in the so-called "Xenos Wars" in which various alien species were exterminated. In M36 millions of Imperial Guardsmen and elements from Battlefleet Validus were responsible for the collapse of Waaagh! Tuskragga.

Age of Apostasy: Thorian forces from the Validus sector waged a long and bloody battle against the pro-Vandire forces. When the armies loyal to Vandire were finally defeated the Thorians moved into the Anargo Sector, supporting the Thorian idealists in their war against the followers of Vandire.

Dark Millennium: After the Age of Apostasy Validus remained a stable sector, providing military support to it's surrounding sectors. The greatest example of this feat is probably the fact that the Imperial forces from Validus are the sole reason why the Cruciatine sector is still under human control. However, the Bolev subsector has weakened due to increasing xenos raids. Eldar Corsairs loyal to the Craftworld Luggannath have been carrying out raids against transport ships. Battlefleet Validus has been deployed to solve this matter.