Towed Artillery or Field Artillery is a category of mobile artillery used to support armies in the field. These weapons are specialized for mobility, tactical proficiency, long range, short range and extremely long range target engagement. Which are well used before World War 2.
In Milihime they are a type of unique artillery that can attack planes and due to high initiative able to fire early. However they are very fragile as a single shot from a light tank can take them down.
Also they can only equip are mainly shells, binoculars (to trigger cut-ins) or pistols.