Related Rule
South Africa
Practice Relating to Rule 14. Proportionality in Attack
South Africa’s LOAC Manual (1996) lists the principle of proportionality among the general principles of the law of armed conflict. It states: “The loss of life and damage to property caused by military action must not be disproportionate to the military advantage to be gained.” 
South Africa, Presentation on the South African Approach to International Humanitarian Law, Appendix A, Chapter 4: International Humanitarian Law (The Law of Armed Conflict), National Defence Force, 1996, § 8(c). This manual is also included in Chapter 4 of the Draft Civic Education Manual of 1997.
The manual further states: “The law of war does not prohibit effective military action. Its purpose is to prevent unnecessary suffering and damage which would afford no military advantage or which is disproportionate to the military advantage obtained.” 
South Africa, Presentation on the South African Approach to International Humanitarian Law, Appendix A, Chapter 4: International Humanitarian Law (The Law of Armed Conflict), National Defence Force, 1996, § 16. This manual is also included in Chapter 4 of the Draft Civic Education Manual of 1997.
South Africa’s Revised Civic Education Manual (2004) states:
35. The following three principles govern the LOAC:
c. Proportionality. The loss of life and damage to property caused by military action must not be disproportionate to the military advantage to be gained. 
South Africa, Revised Civic Education Manual, South African National Defence Force, 2004, Chapter 4, § 35(c).
South Africa’s ICC Act (2002) reproduces the war crimes listed in the 1998 ICC Statute, including in international armed conflicts:
intentionally launching an attack in the knowledge that such attack will cause incidental loss of life or injury to civilians or damage to civilian objects … which would be clearly excessive in relation to the concrete and direct overall military advantage anticipated. 
South Africa, ICC Act, 2002, Schedule 1, Part 3, § (b)(iv).