Siege on Accellis

The Siege of Accellis was an Imperial campaign undertaken by the Storm Sentinels Space Marine Chapter in 773.M40 to the world of Accellis to help recover valuable Standard Template Constructs that had been found by the alien race known as Diggas. The Chapter deployed multiple companies to help with recovery operations and to deter and resistance from the upstart xenos. Unfortunately, the newly discovered STC was kept in a highly secured fortress built by the xenos. Though the Storm Sentinels finally managed to breach the Diggas citadel, unfortunately, they are unable to recover the valuable STC.

History
In 773.M40, Diggas find a collection of rare and valuable STCs on the planet. They begin looting the STCs and use them to take over the planet. The Diggas create a fortress on the planet to protect their territory that spans 12,000 kilometers with layers of crude, yet durable walls. The Storm Sentinels immediately take note of the fortress, but are only able to deploy after the fortress' construction is complete. The 2nd, 4th, and 8th Companies are deployed on the planet, led by Captain Jude Vituris of the 4th Company. The siege lasts for weeks until Terminator Squads and a Strike Force deploy within the walls of the Fortress. This allows the Chapter to destroy the Fortress, but they fail to recover the STCs.