Related Rule
New Zealand
Practice Relating to Rule 14. Proportionality in Attack
Section B. Determination of the anticipated military advantage
New Zealand’s Military Manual (1992) states:
In deciding whether the principle of proportionality is being respected, the standard of measurement is the contribution to the military purpose of an attack or operation considered as a whole, as compared with other consequences of the action, such as the effect upon civilians or civilian objects. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 207.
Upon ratification of the 1977 Additional Protocol I, New Zealand stated that references to the “military advantage” were intended to mean “the advantage anticipated from the attack considered as a whole and not only from isolated or particular parts of that attack” and maintained that the term “military advantage” involved a number of considerations, including the security of the attacking forces. New Zealand further stated that the expression “concrete and direct military advantage anticipated” meant “a bona fide expectation that the attack will make a relevant and proportional contribution to the objective of the military attack involved”. 
New Zealand, Declarations made upon ratification of the 1977 Additional Protocol I, 8 February 1988, § 3.