Practice Relating to Rule 21. Target Selection
In certain circumstances it is possible to reduce the risk to the civilian population and to civilian property if the military commander selects a different objective, from which he can achieve about the same military advantage as from the prime objective. In many situations, however, it is impossible to denote an alternative objective, for which reason the rule concerning second-line objectives has been given the reservation mentioned by way of introduction: “when a choice is possible”.