Significant commentary (here and here) continues to be generated about proportionality and the legality of the use of force, including addressing the jus ad bellum (justification or reasons for war) underpinning Operation Protective Edge. Critical questions are now making their way into the mainstream media asking about the relationship between weapons deployment in Gaza and applying proportionality tests to the actions of all the military actors involved.  In particular, the choice of weapons utilized during the course of hostilities raises specific questions that implicate command responsibility for any breaches of the law of armed conflict. Weapons choice is a logical a priori element of any proportionality analysis, if one examines command responsibility.  Thus command responsibility assessment includes the choice to deploy particular kinds of weapons and is different from a narrow focus on the actions of the individual combatant who uses the weapon in question (though the individual combatant is not exempt from charges of breach of the law of armed conflict for her actions and choices). As one commentator has noted:

Proportionality, however, is a legal term with a specific legal meaning. It is one of a set of fundamental legal obligations that helps to minimize suffering during wartime. The principle of proportionality forbids attacks in which the expected civilian casualties from the attack will be excessive in relation to the anticipated military advantage gained.

Weapons choice is a intrinsic element of measuring whether excessive force has been used and whether meaningful efforts have been made to minimize incidental harms to civilian in the course of military operations. A logical precursor to the evaluation of proportionality and its breach is the an assessment of weapons use and the expected civilian casualties that might follow in relation to the anticipated military advantage gained.  The analysis would clearly be framed by parallel assessment of what choices of weaponry were available to commanders at the relevant time, and whether for example precision weapons could be deployed particularly when force is exercised in densely populated areas. Thus, picking up on Blank (below), the logical corollary of the notion of reasonable judgment is that the steps taken to avoid harm to civilians be subject close and rigorous assessment;

The law also does not require perfect accuracy in targeting. But it does require extensive steps to protect civilians and reasonable judgments about the potential harm to civilians and the actions needed to minimize that harm.

There is general agreement that the deployment of rockets towards populated areas in Israel by Hamas that could not be aimed with discrimination or precision is a prima facie breach of the law of armed conflict.  But, a parallel conversation is emergent on weapons choices by Israeli forces during the course of Operation Protective Edge.  It appears that the White House, the State Department, the United Nations, NGOs and former Israeli soldiers have raised specific concerns about decisions to deploy artillery in densely populated civilian areas in Gaza during the course of the conflict instead of precision weapons where control of targets, specificity, and scatter damage might have been reduced. Weapons are not the only element of precision, but they remain a fundamental building block in assessing discrimination in the methods and means of warfare. As one astute commentator on precision warfare, Michael Schmitt, has outlined:

Precision strikes …  require more than accurate weapon systems. Robust command, control, communications, computers, intelligence, surveillance, and reconnaissance (C4ISR), for instance, can be as determinative of success as the weapon employed.

Schmitt also describes well the specific prohibitions on the use of certain weapons set down by the law of armed conflict:

The express prohibition on indiscriminate attacks is found in Article 51.4 of Additional Protocol I:
Indiscriminate attacks are prohibited. Indiscriminate attacks are:

(a) those which are not directed at a specific military objective;
(b) those which employ a method or means of combat which cannot be directed at a specific military objective; or
(c) those which employ a method or means of combat the effects of which cannot be limited as required by this Protocol; and consequently, in each such case, are of a nature to strike military objectives and civilians or civilian objects without distinction.

Thus, by subparagraph (a), international humanitarian law forbids the indiscriminate use of a weapon, whereas subparagraphs (b) and (c) prohibit indiscriminate weapons. Customary international humanitarian law unquestionably includes similar prohibitions.

Artillery is not a prohibited weapon per se under existing norms. However, the choice to deploy a certain kind of weapon which is quantitatively less discerning and which may contribute to a functional inability to make appropriate distinctions between civilians and combatants, corresponding raises direct issues around proportionality and breach of the material rules of the law of armed conflict. As the International Commission of Inquiry takes up its mandate, it appears likely that this particular issue will be one of the key command and control assessments to be scrutinized.