Legio cohorts are occasionally attached to campaigning Marine Chapters, such as during Operation Carthage (the Second Pacification of Isstvan V). When the Desert Lions Chapter took the planet's defence forts they were preceded by a complete Legio Cohort of Robots. The Robots had been programmed to advance in an apparently mindless fashion, and proved easy targets for the defenders. However, the Desert Lions used the opportunity to map out the defenders' fire-plans and blind spots. In the Lions' ensuing assault only seven Marines were lost.
All the surviving Robots were inducted into the Chapter as honorary members as a mark of respect
From the 20k Compendium.
A parallel could be drawn with Tsagualsa, which the Night Lords made as there base of operations during the Heresy, that was later colonized.