Units are divided into six cells, and furthermore divided into three Front and Back rows. Commanders will dictate which cells can be placed with monsters.
All monsters have an innate range, and cannot attack targets that are not within reach. Spells share the same behavior, and some monsters will have spells with range that is shorter than the monster's standard attack. In this case, spells will never activate and the monster will only resort to using standard attacks.
Where a monster is positioned in a Unit offers lots of strategic options. Placing monsters in the back row makes them less likely to be targeted, but skills that attack monsters in the rear exists. Placing lots of monsters in the front can create an impenetrable wall, but skills that can stun an entire row may render your army helpless.