Under the original concept of the artillery fire support base, a 6-gun battery set up with one howitzer in the center to fire illumination rounds during night attacks and serve as the base's main registration gun. The other 5 howitzers were arranged around it in a "star" pattern. Smaller FSBs tended to vary greatly from this layout, with two to four howitzers of various calibers (usually 105 mm and 155 mm at battalion level) located in dispersed and fortified firing positions. These smaller bases arranged their guns in square or triangle patterns when possible.