From The Heroes of Might and Magic III wiki
- Force field is used to block enemy ground troops from advancing. It is often used in this purpose to protect shooters or at least give them more time to thin enemy troops. It becomes very useful in battle fields with suitable obstacles, that create narrow paths or pockets. Even in a totally clear battle field, with expert earth magic a three wide force field can protect one hex size troops on the edge of the field. Although quite hypotetical situtation, a basic force field can be used to protect troops using defending hero's corners.