The infantry Command is the basic barracks building that produces most of Imperial Guard infantry units.
The IC can be garrisoned by up to 3 infantry squads. In order to produce Kasrkins and Ogryns it has to be upgraded with Kasrkins Quarters and Ogryn Kasrkins respectively.
In 1.73 it's where you can choose one of IG's doctrines.
Amount of garrison slots: 3
Available add-ons: Kasrkin Quarters || Ogryn Quarters